OK, When you have a problem like this, you need to look at the basics. Is the wireless link between the buildings a bridge or a router type connection? If the IP subnet is shared between the buildings? If not, then you have a routing situation. In that case, you will easily be able to connect to directly connected networks, but you need to check for proper settings for the gateway of last resort.
Also, you need to be sure that the router/firewall facing the Internet has a route back to the wireless link.
Check those items, and if it doesn’t solve it, post additional information.