To unban someone in your private Rivals server , the usual method is to remove the block you used on them in Roblox. If you banned them by blocking their account, go to their Roblox profile and select Unblock User so they can join again.

What to do

  1. Open Roblox and go to your private server page.
  2. Find the person you blocked.
  3. Open their profile or the server controls.
  4. Select Unblock User or the equivalent unban option.

Important note

If Rivals uses a game-level ban rather than just a private-server block, unbanning may not be available from your side. Some reports say private-server bans may require resetting the server or using the game’s moderation/appeal process instead.

For Rivals specifically

For ban appeals in Rivals, players commonly use the official Discord/server support route, check pinned messages, or contact the moderation bot for appeal steps.

TL;DR

If it was just a private-server block, unblock them on Roblox. If it was a Rivals ban, you’ll likely need to use the official appeal process instead.