the meet that should have been a full swap but wasnt... what went wrong

so we met this couple from leeds two weekends ago, the chat had been brilliant, all 4 of us were clearly into a full swap, we'd talked about it openly, theyd done it before so had we... then we get to the hotel room and within 10 mins it becomes obvious shes not actually into me. like she was polite but the energy was just gone. we ended up doing soft swap and going home early. ive been replaying it ever since trying to figure out what flipped. were the pics misleading even though i looked the same in person? was it pheromones? was she just nervous and trying to back out? what would you have done differently in the moment