I assume that you're running a wifi router, and you're close enough to it to get a decent signal from it.
Long press the connection to that router. Tell it to forget the connection, It'll scan and find the connection again, Connect to it, giving it any password it asks for. (If you ever connected to a wifi signal with that name, it remembers the security needed for that named connection, If your connection has the same name, but different security, you won't connect to it. Forgetting the connection forgets the name, so you're connecting to a "new" connection.)
