How can I have an evaluation licence for RVDS 4.1 Pro that I have downloaded from
https://silver.arm.com
RVDS was discontinued a couple of years ago, and replaced by DS-5. As it's discontinued, that's why you can no longer get evaluation licenses from the website.
Generally the recommendation would be to use DS-5 (for which you can get an eval license from the website). If you specifically need RVDS I'd suggest contacting ARM's support team.