Companion summon bug

I cannot summon my companion even though I have enough spirit. I also tried the troubleshoot what I found on the internet and forum. Nothing works. Please resolve this bug. I cannot summon my beast companion

I'm having the same problem. I had a quadrilla, then I captured a Winged Horror. When I inserted the wing horror it despawned the quadrilla but the horror didn't appear. But when I tried to swap the skill gems back, the quadrilla didn't come back. So now my mercenary can't summon any companion at all - even with more than enough spirit (e.g. 100-134 spirit with all heralds switched off)

A clue that there's something amiss is that if I tried to upgrade the skill gem, neither companion shows up in the skill tab for upgrading