Rejoin the server and try the potion again
Make sure you are not in a menu or GUI when using it
Check that your inventory has an empty hand selected
Move the potion to your hotbar and right-click it
Make sure you are not in combat, stunned, or otherwise blocked from using items
Try switching to another slot and back
Drop the potion and pick it up again
Relog after clearing any lag or desync
Check if your client mods or macro keys are interfering
Disable any auto-use or item-use keybinds
Try using the potion in a different location
Verify the item is not bugged by comparing it with a fresh one
Restart Minecraft if the item still will not drink
If it still fails, contact the SkyBlock server staff or report the bug