Allow me to share some information about why you’re experiencing this issue and how to resolve it.
Here are the following reasons why you're experiencing this issue:
PDF application is outdated.
Full cache and cookies on your browser.
Recently switched to a different browser.
To fix this, let's make sure that your PDF application is updated then, clear the cache to eliminate the junk files. Alternatively, we can use other supported browsers to further isolate the issue.