Open Core doesnt show second boot drive

[nineniner]

I had clover working with an internal NVME and an external USB SSD both running Catalina. I installed open core and updated the NVME install to Big Sur. It worked, but now my external SSD with Catalina doesnt show up as a boot option (but it is visible in finder and disk utility when I boot into Big Sur). Does anyone have a fix for this?

 

[nineniner]

Just realized it also stopped showing my windows drive as a boot option too.

 

[Edhawk]

Have a look at this section of the OpenCore Troubleshooting guide - # it shows how to resolve not seeing bootable partitions.