I have a 2017 29H as well, and itís driving me mad why the awning sometimes doesnít retract. Iíve never had to manually retract though, as it will eventually work. Itís the LCI Solera, 12v model. The retract takes more power than extend, so I think itís a low battery issue- although you would think being plugged in or running gennie would solve that problem. Iíve never found the smoking gun as to why it wonít retract- but I have found that pulling the pivot points down seems to help. I think in that position thereís less force required to retract (although the manual specifically says you donít need to do this; manuals sometimes lie like rugs.) And if the battery is slightly low, that little bit seems to help.
Iíve been meaning to follow the power lines to see if Thor did something stupid, like connect it to the chassis battery instead of the coach. Thatís the only thing I can think of that would give these symptoms. If thatís the case, turning on the engine would help.
Hereís our manual retract page, btw