i have a longsword +5 and i can use a +7 and noone will upgrade it for me is this a but or am i missing something my crafting is 38

Upgrading the Enhancement value of a weapon takes more gold for each additional increment, and if you don't have enough gold on you, that menu choice doesn't appear in the dialogue.
I think Marty at the outpost will only boost a weapon to +5, after that you may need to talk to the Beholder in the Hall of Mirrors.
After that you need to find the smiths in the more difficult dungeons.