I think I have followed all the instructions at https://docs.moodle.org/dev/Third_Party_Libraries#:~:text=A%20third%20party%20library%20refers,php%22.
But it does not appear in the Site Administration -> Development -> 3rd party libraries.
I have cleared all caches and browsed to to admin index page, I have increased the version number on my plugin and re-loaded.
I have checked my thirdpartylibs.xml against other plugins and mine looks the same format, but I did notice none of the blocks plugins had one.
Any idea what I have missed.