Payplan Apps - not working with latest version of Joomla 3.8.6

Hi There, we recently upgraded Joomla to version 3.8.6 - and after which we were unable to download apps through the Payplans store or make any new app installments without the site going down page by page. Whilst amends were being made we tracked the problem to definitely being the payplan apps.

Do you know how this can be amended and when we will perhaps receive an update for Payplans to work with the current latest version of joomla?

Thanks,