If using Lunar Client, follow and make sure the "OF" (optifine) is selected.
If using a different client or custom setup, "Optifine" is required OR "CIT Resewn" on Fabric.
The skill bar, health bar, or hotbar looks messed up!
If using LunarClient, read . Follow step 3 and 4.
If using another client or custom mods, you've adjusted your bossbar or GUI scale somehow. Try turning off anything that sounds like "Custom Bossbar" or "GUI Scaling". On Vanilla, this should work fine so try the recommended .