Billing module not finalizing invoices

Sup folks,

For some reason or another I am unable to finalize invoices. When I click finalize it just scrolls to the top of the page. I'm not getting any errors or anything which makes it hard for me to try and figure it out.

Thanks

 

I get the following when I try to finalize the invoice:

Code:

POST https://localhost:8080/billing/invoice_edit.php?action=finalize_invoice

Status
500
VersionHTTP/2
Transferred589 B (1 B size)
Referrer Policystrict-origin-when-cross-origin
Request PriorityHighest
DNS ResolutionSystem

I get that in the developer tools in firefox. I'm using ISPConfig 3.3.1 and billing_addon_2.0.17