cannot cast spells in combat or in camp both mage and priest spell

When you cast the spell, are you typing in the spell's name correctly?

Also, check your spellbook to make sure the character actually knows the spell you're trying to cast and make sure the character has a spell point of the correct level.

Don't forget that characters under disabling status ailments (including paralyzed and dead) can't use spells.

(You neglected to mention which game you are talking about, so I am assuming you are referring to a computer version of one of the early Wizardries.)

Forget that you have a mouse.
For interacting with environment (chests) and spellbook, you must use the confirm button on keyboard or controller.