Because the 1.0 Launch version of V Rising is incompatible with the old servers, your old servers won't appear in the Load Game menu. But there is no need to worry!
You can still play on your old servers by switching to the previous version of V Rising. However, this means you won't be able to access the 1.0 Launch content.
To play on a server created before the 1.0 Launch:
1. Right-click V Rising in Steam
2. Select Properties.. > Betas
3. In the dropdown, choose the branch for the earlier version you would like to play:
For V Rising Early Access, choose the "legacy-0.5.x" branch
For the Secrets of Gloomrot update, choose the "legacy-0.6.x" branch
4. Update V Rising and play as usual
To return to the 1.0 Launch version, follow the same steps and choose "none" in the Betas dropdown menu.