>> when I reboot it can't find or read its

>>     ~/.Mathematica/Licensing/mathpass
>> file [that] contains the activation key.

The Mathematica license file generally needs to be copied into

    .../mathematica/13.1.0/Configuration/Licensing/mathpass

manually.

In my environment, we have a central license server, so client systems
have a simple one-line mathpass file that starts with an exclamation
point, followed by the hostname of the license server.

The license server itself has a mathpass file with additional fields
that encodes more information, and also records the license expiration
date.

----------------------------------------

P.S. Mathematica 14.1.0 was announced by the vendor a few days ago.

-------------------------------------------------------------------------------
- Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
- University of Utah                                                          -
- Department of Mathematics, 110 LCB    Internet e-mail: beebe@???  -
- 155 S 1400 E RM 233                       beebe@???  beebe@??? -
- Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe/ -
-------------------------------------------------------------------------------