After i ugraded Mr. Houses robots i returned to the north strip gate and cannot get in. it requires a key and ive been in it before and i have 2,000 caps.

please include this in patch or any suggestions?

Try taking the train from Camp McCarren?

It's a bug, reload an earlier save, some doors seem to become locked and require a key for no reason, doors that have no business being locked.

If ya can't reload and can't use the monorail (like me!) then ya can try killing the securitrons as they apprently have a key. If they don't well ya stuffed until patch , like me!