Fifth wheel would not release

Here is the Holland owners manual for that 5th wheel. Pay particular attention to lubrication requirements on pages 12 and 13. Do you take the 5th wheel plate off the tractor every 60,000 miles, thoroughly clean it and re lubricate according to the diagram? I didn't think so.
Have you ever seen anyone adjust a 5th wheel using the tools (Holland part #4000171)and procedures as described on pages 15 and 16? I didn't think so. That should also be done at 60,000 mile intervals.

No one ever does any maintenance to a 5th wheel. Just slobber some grease on there and hope for the best. These things do wear, and can be adjusted for that wear without an overhaul required. Finding someone willing to do it and the attendant liability issues are another matter.
https://www.anythingtruck.com/instructions/370-FWS1-Owners-Manual.pdf