Look to the messages tab of your ground control software (Mission Planner or QGC) and see what other messages appeared. There should be something to tell you what arming check did not pass.
Do not disable arming checks. They may be a bit of a pain, but they’re there to help.
Do not force arm unless you know what you’re doing, or why you’re doing it. Failing an arming check is not normally a good reason to force arm.