Activating renewals and checking new versions broken in FileMaker 13

We have recently discovered an issue which is preventing some BookingPOINT customers from activating their renewals or checking for new versions. When affected customers click on the 'Activate Renewal' button, they get an error message stating "ERROR: An error occurred while trying to renew. Please try again later or contact Hi-Voltage for assistance." Likewise, when clicking on the 'Check for new version' button, they get a similar error message. Upon investigating the issue, we have discovered the issue only occurs in FileMaker 13, which is obsolete and no longer supported by FileMaker. To overcome the issue, we ask customers to [...]