Sequoia running fine on iMac "Core i5" 3.4 27" (5K, Mid-2017) UNTIL POWER FAILURE

I used OCLP to install Sequoia on my 18,3 imac. It worked great until there was a power failure. Now when my Mac boots, it sees the Sequoia boot disk as an incompatible OS. In the lower right hand corner of the Startup Manager screen I see "REL-104-2025-03-04"

It is as if OCLP is not loading during startup.

Thanks for any advice.