swapped a drive in my drobo and new drive not recognized

I have a drobo 5D and it was close to full with 5x4TB drives in it. I purchased a few new 8TB drives and pulled one of the 4TB and replaced with a new 8TB. The drobo went into protection mode and started the rebuild as soon as I removed the 4TB drive but refuses to mount the new 8TB. I’ve pulled it out and re-seated it, even tried the other 8TB drive (to determine if the drive was the issue) and then for a last straw tried putting the original 4TB drive back in - nothing…still a solid red light and a ‘bay is empty - please add a new drive’ note in dashboard. Any ideas???

hi, if dashboard is seeing a used bay, as though it is empty, it might be worth trying to exit dashboard and relaunching it,
does it still show it as empty if you try that?

it could be that the backplane is somehow faulty in terms of connection, but if no other lights are flashing, and aside from the above, if the drobo is still in a stable state, it might be worth trying to use dashboard to shutdown the drobo and then to power it up again (essentially restarting the drobo, but via dashboard)[hr]
btw how long did you leave that 8TB insisde? it could just be that it needs longer, such as a few hours after the lights stop flashing