Upgrading Payplan Apps with Joomla 3.9???

Hello, we are having a rather difficult time getting the site to the proper format after upgrading. The main problem now is that we cannot get the nice simple tab format registration to show. Regardless of our customizations (adding some extra fields), the original site used a payplans app to make the registration form simple and easy - see attached. We did not customize this tab format - it was part of the quick registration app. Unfortunately, we cannot get to this to work on the upgrades site after many attempts.

Further investigations on our part show that your apps only work witih Payplans 3.7 and Joomla 3.7. The current Joomla version is 3.9 and wonder if this is why we are not getting the same results as before.

SHOULD WE UPGRADE THESE APPS EVEN THOUGH WE ARE AT 3.9 Joomla????

Please let me know.

Thanks

Martin