You can do the following solutions

1. Go to WHM -> Clusters -> Remote Access Key.
It will automatically create remote access key on your server. Just access to it, don't need to generate the new key. After that try to setup it again via RVglobalsoft Manager -> Theme Manager.

2. Try to force update again using this command.

rm -f /usr/local/cpanel/Cpanel/rvversion
perl /root/rvadmin/auto_rvskin.pl

3. If you still have the problem.
Please verify that the key in the file /root/.accesshash and /usr/local/cpanel/Cpanel/rvwhmkey is identical. And check the error on /usr/local/cpanel/logs/error_log

4. If nothing help, please submit support ticket and include the result of these command.

ls -al /usr/local/cpanel/Cpanel/rvwhmkey
ls -al /usr/local/cpanel/Cpanel/rvbin
more /usr/local/cpanel/Cpanel/rvwhmkey
more /root/.accesshash