oof, i was in a really bad reading slump that lasted YEARS, but i got back into it by reading shorter books, easier to read in terms of style/genre/plot...
revisiting older books you've enjoyed can be helpful, but my biggest advice for you (and what helped me the most) would be to switch things up, e.g. if you'd normally only read physical books, try ebooks instead (or vice versa), read during a different time of day than the one you're used to, create the perfect settings in which you could concentrate and focus on the book (maybe play some music, like... background noise/instrumental/classical etc.?) and making yourself physically comfortable and cozy; and most importantly, don't put too much pressure on yourself to read/finish something if you're not enjoying it. it's not really worth it tbh.
anyway, i hope you manage to get back into it and find what works best for you. i wish you good luck :)