Replaced failed hdd, now all drives show up red

After a single drive failure (#3 of 5) with 1 drive redundancy I replaced the failed drive with a new one. Nothing happened, so I rebooted the drobo. Now it shows all drives red and dashboard shows this message:

“Too many hard drives have been removed. Please re-insert the removed hard drives.”

I used it for years without problems and now it seems it lost all my data, support doesn’t want to help (device too old) and recovery costs over 8000 euros.

Any help would be greatly appreciated.