Can you give more details about your router, settings, etc?
You will get that flash code if you are trying to blink the imp up to a 5GHz network, for example, or one on a channel it doesn’t support (if you are in europe, but using a US imp, it will only work if your router is on channels 1-11: it cannot “see” channels 12 or 13).
Sounds like it could be re-selecting its channel to 12 or 13, which means the imp then cannot connect. Unfortunately, the EU spec imp001s are not widely available… imp002’s you can get from digikey.