If all else fails, maybe joining academic groups on Facebook or LinkedIn could help. Sometimes people in those groups share resources. Alternatively, academic help sites like Course Hero might have the solutions, but again, those require a subscription.
Maybe the 4th edition is a newer edition, so there are no official solutions yet. In that case, looking for lecture notes or problem sets from professors who use this edition. If they have a course site, sometimes they'll have solutions to specific problems or at least provide hints and tips. For example, some universities have open courseware, like MIT's OpenCourseWare, but I'm not sure if they use Liboff's book. Let me check. No, it seems they use other textbooks like Griffiths or Zettili. If all else fails, maybe joining academic groups
Quantum Mechanics is a tough subject, and having the solutions can be really helpful for understanding the material. I remember that professors sometimes use specific textbooks for their courses, and if Liboff's is the one here, then maybe the 4th edition is common. The problem is that getting the solutions for this edition... I wonder if it's widely available. Maybe the 4th edition is a newer edition,
Also, maybe solving the problems is part of the learning process, and relying too much on solutions can hinder understanding. Using the textbook's worked examples and checking with peers or instructors for feedback could be better in the long run. But that's a personal choice. For example, some universities have open courseware, like
Also, considering that Liboff's book might have different numbering between editions. So solutions for the 3rd edition might not match the 4th, which complicates things.