Firmware versions of M2s and Bees need to be consistent – falling this, connectivity can be strained. If the failure is due to a firmware version mismatch, you will have to downgrade the M2 to the Bee’s version first. Then upgrade your Bees to the latest version and then re-upgrade your M2 back to the latest version.
Instructions for resolving a firmware version mismatch can be found here.
If the failure is not due to a firmware version mismatch, please try an offline firmware upgrade. Instructions can be found here.
If neither of the above steps resolve the issue, please email email@example.com.