Access Denied

Sadly, you do not currently appear to have permission to access
https://arxiv.org/pdf/2103.13740.pdf

If you are using the PDF Plug-in, it has many bugs and is forbidden here
due to problems it causes at the server end.
You must confirm that you have disabled it before access can be restored.

In Netscape try
Edit -> Preferences -> Navigator -> Applications,
look for Portable Document Format and uncheck the plug-in box.
Or delete the pdf plugin dll file from the
Program Files/Netscape/Navigator/Program/plugins
directory and restart browser. Or for Acroread4/Explorer5 users,
go into Acroread’s
File : Preferences : General : Web_Browser_Integration
and make sure the little box is unchecked.

Note to MacOSX users: There is a bug in the Acrobat reader which
causes it to make endless streams of requests after having
successfully downloaded the full pdf. Note that it is not necessary to
use Acrobat at all, since pdf’s from here render as well or better
in the default Preview.app on MacOSX. If for some reason you think you
need to use Acrobat, go to Acrobat Preferences -> Internet
and turn off the
“Allow speculative downloading in the background” option, which comes
(incorrectly) turned on by default, and whose behavior is quite broken.

If you believe this determination to be in error, see
https://arxiv.org/denied.html
for additional information about restoring access and detailed guidelines for harvesting arXiv content.
[UPDATED: 12-18-2019]