I’m not familiar with this printer, but some diagnostic information might be useful. I assume it was working for you prior to the latest update you did?
Share lpstat -t
Enable CUPS debug logging with sudo cupsctl --debug-logging, then try printing to the SL650. Check /var/log/cups/error_log for the messages from that print attempt. It can contain lengthy output (sometimes I delete the file before sending a print job). Something like the following might help filter for something pertinent to the issue hopefully…