What Mac are you using?
iMac (Retina 5K, 27-inch, Late 2015)
Model Identifiers: iMac17,1

What version of OCLP are you using?
2.3.1

What OS version do you have installed or are trying to install?
Installed: Sequoia 15.3.2 (24D81)

What exactly is the problem you are facing?
After installing OCLP 2.3.1 to disk my iMac refuses to boot. At boot I press the Option key to get the menu I choose the blue OCLP icon. Normally it proceeds with the apple logo but now it shows a circle with a diagonal.
Luckily with my old USB stick that has OCLP 2.2.0 I booted of my USB. That worked fine. Then I mounted my EFI removed the OC folder and replaced it with the one from my USB stick. So now my iMac boots again but with 2.2.0
Use the tool: MountEFI Available on GitHub: https://github.com/corpnewt/MountEFI

Now I have been able to fix it with the following settings in OCLP:
My iMac is a late 2015 27" with Model nr 17,1

In the OCLP utility in settings I put:
Target Model: 17,1
Build: Debug: Check all 3 options: Verbose, Kext Debugging and OpenCore Debugging
Extra’s: Check: 3rd Party NVMe PM
Security: Check all the options under SIP
SMBIOS: SMBIOS Spoof Level: Moderate and SMBIOS Spoof Model: iMac19,1
Then I Build and Install OpenCore to disk


By the way in the mean time OCLP was updated to 2.3.2 and I used this version.

Reboot.

And voila it works!