I created a character who’s proficiency bonus isn’t showing up on the melee weapons attack die. Even though the weapon is one that the character is proficient with. Is there any way to fix this or am I interpreting it incorrectly?

You have worded that in a way that it describes the problem, but does not give any details (like at all, I'm impressed).

Can you post a link to the character (share link for us, URL for mods to check character directly)?

To start with, what class and level are you, what weapon are you using, and what number are you seeing in the sheet?