
Hi there,
I'm Cherrelyn and I'm here to help.
Please try repairing Office from Settings > Apps > Microsoft 365 > Modify > Quick Repair first. If that doesn’t work, check your default printer set it to “Microsoft Print to PDF” temporarily and restart Excel. Also, sign out and back into your 365 account to refresh the connection; sometimes a stale login token can block PDF generation.
I hope this will help and if you have any question please feel free to ask.
Warm regards,
Cherrelyn