Power was shut off to my house for 2 hours. The PC shut down once the UPS power ran out.
Once the power came back up there appeared to be issues with my Lenovo X3650M5 saying there was drive issues. Finally cleared this and got it to boot up.
The software went through and rescaned all the alerts which took ages. During this time 2 of my 4 cameras had no signal while the other two were fine. After about 30 minutes one camera came back online and was working fine. The other did not.
So I went and edited the camera and rescaned it. Detected the camera okay and then went through the rainbow pattern and camera came to life. This lasted all of 20 seconds and it went back to no signal.

The camera is working and I have checked through the IP address with a browser. It is an older Reolink which requires the adobe flash player so can't see the screen but as I did get a picture for 20 seconds have to assume it is working.

I cannot get the picture back even adding the camera again so am now stuck.

Any suggestions as to how to get the signal back?

I am wondering how you know for sure that the camera is still working when you can not view it on it's web interface! A 20 second flash of picture may just as well have indicated the camera dying, I have had to replace 2 very old cameras that I could no longer get to the web interface due to out of date firmware and certificates etc, and what a difference a new camera made, I should have replace the crap cameras long ago!

Oh the camera is working just fine. I hooked it to my Synology and it displayed a picture fine.
Half way through today my Lenovo X3650M5 once again failed through the IMM and same warning message of "The following VDs are missing: 000"
Was able to once again clear it and rebooted the server.
This time all four cameras once again working.

Not sure what is causing the issue with my server as it reports all the drives are fine and all the virtual drives are there. Can't find any info on it one the net. Beginning to think my server is about to go belly up. Does not explain why BI would not display that one camera.

Just to clarify, is your entire BI system virtualized or is it running directly on a Windows PC!

It is running under Windows 11 on my server direct. Used to have it virtualized but had the server spare so went for the un-virtualized way.
The drives are controlled by the RAID controller and are passed through to the OS depending on how they are set up. I just have them set up as RAID0 and pass each of the 3 VD's (virtual drives) to Windows. All 4 cameras still displaying after 24 hours. Will monitor but there have been two BI updates since then.

I would strongly suggest that you turn off the auto updates, as they are essentially beta versions, stick with updating to the stable versions, when you have time to investigate any changes and deal with any issues that may arise! Or perhaps you enjoy a little drama in your life.