Failed to claim device: Device has already pending transfers

Yon can only claim a device when it is breathing cyan (or magenta when in Safe Mode).

The orange blinks may indicate some issue with the device keys and/or connectivity issues when your network does not permit a cloud connection (firewall, proxy, …).

The keys issue can be solved via CLI and DFU Mode

particle keys server
particle keys doctor <insertYourDeviceID>

To mitigate the connectivity issue you can try to connect to some other WiFi (e.g. your mobile phone hotspot).