Breathing Cyan "Core not found. Check that it is online" when using Build

Hi all,

I think my Core is properly set up because it is breathing cyan, and I have created a simple blink program using which compiles correctly.

However, when I try and flash it, after a couple of minutes and a “This request is taking longer than usual, please be patient”, it does not flash the program.

Any ideas?


@ChrisLewis A couple of things to try:

  • Do you have multiple Cores? If so, are you sure you have selected the right one? Check the ‘Cores’ menu in the IDE and hit the star next to the one you want to flash.
  • Try resetting the Core so it re-connects, it’s possible the connection died but it’s not showing that it did for some reason.
  • If you hit “Reflash Tinker” in the mobile app, does it download the Tinker firmware successfully (flashing magenta for a little while)?

Hi Zach, thanks for the reply.

I do not have multiple cores, and after resetting (still breathing cyan) reflashing tinker appears to have no effect!

I do eventually get an error: “We have encountered and error” and a link to, with a code of 504.

Hey @ChrisLewis,

If you wanted to email me at I could try to help. Would you be willing to send me your username and your device id? I can check the logs and see if wires are getting crossed.

If you haven’t already, you can get your device id by putting the core into listening mode (flashing blue), connecting to it over serial, and hitting “i”. I can give you better serial instructions if you tell me what operating system you’re using.


Hi David, I have sent an email.

I’m having essentially the same issue. I get the breathing cyan LED. When flashing to the core through the web IDE, I’ll either see a message about it taking longer than normal, or it’ll throw an error about timing out, or just say ready. During these reflashes the LED never stops breathing cyan. Disconnecting power and powering back goes from blinking white, to flashing green, to solid blue (maybe - it’s very brief), to breathing cyan.

After powering back up the iOS app shows the core as being connected. Doing anything pin related times out. If I try to reflash Tinker I get the following error:

Internal Error

An error was reported by the Spark Cloud. Please try again later. If the issue is not resolved, please visit for help.

The breathing cyan never changes when trying to reflash Tinker.

For what its worth, on another Core I’m able to reflash Tinker without issue. Also, the Core that is stuck breathing was operational earlier. It was only after trying to flash the “multiple LEDs” example that it started misbehaving.

Coincidentally, the website wasn’t fully working around the same time. I’d sent the link to to a friend and he said it was down. When I checked the site, only the first background image loaded. Related?

I was having the same problem as Chris with the IDE saying

“This request is taking longer than usual, please be patient”

and reflashing Tinker with the iOS app gave me

An error was reported by the Spark Cloud. Please try again later. If the issue is not resolved, please visit for help.

Holding the mode button down didn’t do anything. I messed around with it for hours and now it’s working. I’m unsure what exactly I did to fix it, but I did hold in the mode button for 10 seconds while powering up and this restarted everything and I entered my wi-fi details with the app and it started working correctly. BUT, I tried this 10 sec on power up thing probably a half dozen times before I got to where I am now.

I have a feeling there was something corrupted that eventually got rewritten with the correct value and now it works. I’ll gladly provide more details if they can stop this issue from appearing for other users.

Hey guys - I think what’s happening here is that the user application that you previously installed is blocking the firmware updates from coming through. @buffington and @Dillon1337, had you programmed the Core with an application that had some long delay() in the loop?

This is something we need to fix, but in the meantime, try to keep the total length of delays in the loop to no longer than a couple of seconds.

Hi Zach,

I think you are right about delay(). I was working on a 500ms LED blinker (similar to the Arduino sample) when the Core stopped being flashable.

Saying that, I followed instructions from David to factory reset the core and now I can use Tinker as normal.

Thanks for your help!

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@zach I started seeing the problem after trying to flash the “control LEDs over the net” example. That said, there’s a chance I might have tried flashing something prior to that with a long delay. I see if I can reset the core a bit later and recreate the issue.

thanks @buffington, keep us posted!

I thought I would provide my feedback and say that I had this same error in the subject description. Factory reset, then re-sync with android app and problem solved.

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One more bit of reflection: Out of habit, my LED flashing code contained a while(true) loop within ‘loop()’, which looking back seems like madness! Removed it and now my delay(1000); statements do not stop flashing new code anymore.

Hey guys, just created a new thread for this issue:

Great, thanks for the continued communication on the issue.

So I have the same issue - Error: Core not found while it’s “breathing cyan”

I tried holding down mode and taping reset - no luck… It went through the white cycle and turned amber.
I then tried powering off and on, and this time it booted up in listening mode, and I attempted to connect to it again, but still I have the same issue - Error: Core not found. The last piece of code I flashed had delay(2000) for the humidity sensor that I was attempting to use.

What is the best way to reset it?

@kidrock The two things to try out at this moment would be:

  1. Factory reset the core, connect to WiFi and then Reflash Tinker using the iPhone app
  2. Connect the core over USB:

This might not apply, but make sure you click ‘Verify’ before flashing your code. I think we have a bug right now where compile errors won’t show up during a flash that will show up during a verify.

Code verifies fine, I reset it, re-flashed tinker and now and up and running again!

But I am unable to get the Spark Simple Web Interface working (Error: roh roh), dunno if it’s related to the cloud connectivity.