Log in with your Adobe ID and Password(Adobe ID is your email id registered with Adobe). Check if you can access the service.
If the issue persists, you may try a different browser, or a different machine, or check on a browser on your mobile/handheld device. If the issue is not reproducible on another machine/device, check with your IT if there is a firewall restriction on your primary device/machine.
Using Adobe Acrobat Reader DC:
Make sure you are connected to the Internet and have no firewall restrictions.
If Reader is already installed, and you are accessing the ExportPDF service through it, then try signing out and sign back in with your Adobe ID and password.
If the issue persists, try the above step on a different machine, or on mobile/handheld device. There are limited services that we can access through Adobe Acrobat Reader app on mobile/handheld devices. The other services can be accessed with a browser as mentioned in above section “Using a browser.”