WEP networks are a little special, as well as insecure! When specifying the password, the WEP hex key needs some additional details beyond just the basic hex key.
To setup WEP on the Photon requires you add some extra information to the WEP password that’s required by the WiFi module. The WEP key should be provided with this additional information:
 the index of the WEP key (03) as configured in your router. (in your router administration pages it’s probably labelled 14, so just subtract 1)
 the length of the key in bytes, 5 or 13 bytes for 40bit and 104bit keys respectively.
 the key itself
For example, let’s say we have the key 123456789A at index 0, then this would be written as

00
 this is the key index 0. Other possible values are01
,02
,03
. 
05
 this is the length of the 40bit key (5 bytes  it’s the number of letters/numbers in the key divided by 2). Another possible value is0D
for 104bit keys containing 26 characters. 
123456789A
 the remainder is the actual key
Putting that together we get:
00 05 123456789A
or written without spaces (as it should be)
0005123456789A