I'm pretty sure he didn't fail the medical. I think Liverpool tried to use his medical history to chivvy something off the price - knowing they had Shaqiri at 12m as a back up.
The two reasons Nabil Fekir didn’t sign for the Reds
Melissa Reddy has outlined the two reasons that Michael Edwards and Jurgen Klopp decided against signing Nabil Fekir from Lyon in the summer. The Reds were on the verge of announcing the signing of…www.empireofthekop.com
I understand the reticence where a player has ruptured his knee is concerned, but he was only 21 (2015), and he's played a lot of football since then. I think last two years Harry Kane's probably missed more games than Fekir.
There aren't too many players bobbing around Europe with his ability and productivity (and versatility in forward areas) - when you think what 30m gets you now, if the knee holds out, that would be an absolute bargain.
Yes it's the " if the knees holds out" which is the problem - no insurer will take him on giving full cover for he knee in the case he has to give up football.
That's why bigger clubs won't take he risk. Betis get a player that they can only dream of plus about 20- 25m cash left over after selling Lo Celso so whilst there is risk they are far better off than before they bought Lo Celso 4 months ago and that's why the risk makes sense to them.