If you can't log into Silver Server, you probably need to merge your Red & Blue accounts.
You can merge them in the dashboard, make sure to select the right server as your main server.
https://dashboard.pokemonrevolution.net/dashboard
If you're still unable to log into Silver after merging your account, you'll have to reset your password on the dashboard.
For more info about the merge and about the errors that might occur with it, take a look at the following link:
https://pokemonrevolution.net/forum/topic/90465-everything-about-the-merge-general-faq-issue-faq-read-before-making-a-merge-issue-thread/?tab=comments#comment-517409