My password is not accepted because it is too long
In password security, the longer the better. With a password manager, using more than 24 characters is simple. Unless, of course, the secure password is not accepted due to its length. (In this case, through STOVE.)
Possibly indicating cleartext storage of a limited field (which is an absolute no-go), or suboptimal or lacking security practices.
In my opinion, an acceptable password length should be L in ln(alphabetSize^L)/ln(2) = (B bits of entropy). For a Bech32 character set (since it excludes ambiguous characters), alphabetSize = 32. A good password should have been 96 and 256 bits of entropy, with 128 bits being my personal preference. This means L = (B)*ln(2)/ln(alphabetSize) = 128*ln(2)/ln(32) = 25.6 = 26 characters.
That's… pretty close to what OP said they were restricted to, so maybe the person who set the 24 character restriction used a similar methodology.