Hi Gmac, fellow gain owner here. Some of my suggestions may sound obvious, but the instuctions for the iwoc modes are not the best.
I assume when pairing the assistance levels were showing in the app. 0,1,2,3 if so good start. Though a connection issue despite them all being checked would seem the obvious fault.
On my version I only have the iwoc 1 controller on the bike and you cycle through the levels, starts at switch on at level 1 green, quick press it flashes, another quick press while flashing, moves it to the next level 2 amber, same again to 3 red and back down to 0 no assistance which is white. The level zero, no assistance can be confused with full charge as they are both white, comparing with the level on the app will confirm what level status you should be in.
Assuming the levels are showing correctly, the engine section of the app should show 100% from the factory for each level. However this may have been inadvertantly set to zero so no assistance. This would be strange but a possability.
Another problem is it may have been in demo mode. This only alows a certain amount of milage to be put on the bike before it cuts the power. This needs the dealer to deactivate I think, but others may be able to confirm if this is the case.
Another trick may be to reset the system. You do this by holding down the iwoc button at switch on for 30 sec. This certainly works for several minor faults such as connection to the app or the odd not switching level malfunction, so may be worth a try.
Frustrating for you, but once sorted you will love it so please persevere.