Have you tried connecting with the computer assistant program.
https://www.dji.com/mavic/info#downloads
You might try re-linking but if firmware isn't installed properly it might not do it.
https://www.youtube.com/watch?v=G52F4hlR4MA

The supplied short cable is fiddly and not very strong and it's better to use a good data cable in the bottom USB.
You must have side cable removed or this won't work.