please let us know which activity, package you are using.
is this a data issue? i mean, is the PDF you are trying to read/export is empty or something? can you validate?
coz, if it was working fine until now, it should do something with the data
I Just tried and activity is working fine.
So there s no issue with activity.
You have to check the package installed.
Can you please reinstall the pacckage by going to manage packages, and either uninstall / install or upgrade to latest version and check if it fixes.