Stuck in 1st gear

If you have a detent ball, then you have an early side-cover. Pre-1971.
See if you can engage two gears, simultaneously. That would be bad and means the interlock pin is missing or way too short. If you can just move the second lever a tiny amount with the first lever shifted into any gear, that is probably normal, That interlock pin is supposed to prevent over-shifting , in addition to preventing selection of two gears at once. The pin has to be in there
Unless you have a shifter with shift stops on it ... like the Hurst Competition Plus. But you still have to adjust those.... lol.