I am currently using v3.99 on PrestaShop 8.2.1. Re-installed 3.99 after 3.995 would create error 500 in backoffice when editing blocks.
HTMLBOX Pro appears to be working, however, when troubleshooting a different module, I enabled debug. While my custom hooks appear correctly in front office (3 different blocks on the product page), Debug reveals two errors prior to displaying the blocks. Errors are:
Warning: Undefined array key "hideblock_by_group" in .../smarty/compile/classic/dd/b2/52/ddb252f6afeeb40ae3213c908b2dfbfe21fb623f_2.file.html.tpl.php on line 557.
and
Warning: Attempt to read property "value" on null in .../smarty/compile/classic/dd/b2/52/ddb252f6afeeb40ae3213c908b2dfbfe21fb623f_2.file.html.tpl.php on line 557
Looks like this could be part of your html.tpl, as that is the only file I could find that contains the hideblock_by_group.
Is there anything I may be doing wrong?