You'll probably need to add some post processing step. Based on how your map looks I'm guessing you're using wave function collapse or something similar. This is a good video (below, go to 17:20) that talks through wave function collapse that I used to develop our lectures about it. I've linked the time step where he talks about doing post processing to add doors to unaccessible areas. For now if you just want something quick and dirty you might just try either adding a walkable path all the way around your map. Or alternatively you can try having a set path through the middle or something that every area has to connect to, so there's always one open space they're all connected to.