Roll20 only supports Firefox and Chrome, non-test/beta versions. This may explain your Pale Moon user's issues. Can your other player please follow Steps 1-3
of our Solving Technical Issues checklist (confirm using the latest non-test version of Firefox or Chrome; turn off all extensions, addons, and anti-virus; and clear the cache) to see if
one of those components is causing the problem? We can only help if we
can recreate the issue, so it is important that you follow each step. If doing that fixes the issue, just let us know. Otherwise, move on to Step 4 , and we'll need all that information, especially the console log starting from before loading the table to where the problem is replicated, to further assist your player.