I had the same fault on my M8. Took the battery out and left it for a day. I also changed the SD card. Put the battery and a new card in and the shutter finished its cycle and worked perfectly until I sold it over a year later.
Here is what I think. The firmware is basic and uses a simple 'state machine' principle that it must complete each state before moving on. If, like me, your SD card is suddenly defective mid-write then the cycle cannot move to the next state and a shutter fault shows.
Incidentally, it was a SanDisk card and I switched to Kingston thereafter.
Of course, in your case it may be a genuine shutter fault. It could be dirt on the shutter blades, which if you can get the shutter to actuate again will eventually disperese, or it could be the shutter fault I had where a recharged battery and a new card is all that was needed.
Hope it resolves itself.
LouisB