Lately we've been having some bugs in the backend where our customers suddenly are unable to complete payments through our HiPay payments gateway and don't even receive the payment e-mails even though paypal still works. Other than that, when we try to change the order status it takes more than one attempt until it finally changes.
I went to check the error log and this is the output I got.
[05-Sep-2021 20:58:38 Europe/Lisbon] PHP Fatal error: Class 'Swift_Preferences' not found in /home/boutiqu6/public_html/tools/swift/preferences.php on line 9
How can I fix this? No changes were made that would let this happen