Senior Cat Accidents?

I'm having an issue with my 14 yo male cat, and I'm hoping someone can give me advice or answers. He's recently starting urinating on my couch. He has never done anything like this before. I took him to the vet and she didn't have any answers for me either. Blood tests came back good. Except for a 2.5lb weight loss he is in great shape.

Nothing in our home has changed at all for him to be stressed. And I've been keeping his litter box immaculate. Which is located in a quiet spot in the basement. We live in a three floor home and so far he is good with the stairs. I can't think of any other issues to bring up.

Thanks in advance for your help!!

I would try putting another litterbox on the level where the sofa is. You may not think he's having issues with the stairs, but the convenience of another litterbox near where he's going inappropriately might solve the problem. I have litterboxes on both the main level and in the basement. The only time I've had an inappropriate urination issue was when Lola had a UTI. Good luck!