I use PTO in both Win 10 and Linux but don't have a problem whether I open it with Firefox or Chrome.  Tabbing will only move the cursor to the next field.  I don't use Mac with PTO, so I can't tell whether that's an odd behavior in Mac OS.  You may like to try another PTO-supported browser instead.  Regardless, you should always open PTO only in a private tab as that helps avoid most common issues.

If you'd like to report a technical issue, you will need to contact Technical Support when they reopen.  This is a peer-to-peer community; your feedback here won't get anywhere.