MP 1,1-5,1 Startup manager no longer accessible trough option key on Mac Pro 5.1 trying to install OpenCore

[Zowan07]

Good day everyone,

I have a Mac Pro 5.1 on which I tried to install MacOS Monterey, With the help of OpenCore patcher.
I followed the Youtube tutorial from Jessie's Flying with an USB key on a new SSD, everything went good until the part were it was supposed to install Monterey where it suddenly powered off.
Since then there is no way for me to have access to Startup manager with option key again, all I have is a white screen with cursor.
I tried with the original SSD with High sierra, without USB key, without the mouse aswell and finally with multiple keyboards, no changes.
It is like it tries to access to it without success, I even waited 2 hours with that white screen without any fortunate changes.
I also proceeded to a Pram and NVram reset, no changes...
Did I broke or missed something? How can I fix? Without having access to Startup manager there is no way to install Monterey on it...
Thanks in advance.

 

[tsialex]

Did you replaced the GPU?

A non-flashed PC GPU does not have pre-boot configuration support. For pre-boot configuration support you need an AppleOEM GPU or a PC GPU flashed with macEFI/EnableGop.

 

[Zowan07]

Did you replaced the GPU?

A non-flashed PC GPU does not have pre-boot configuration support. For pre-boot configuration support you need an AppleOEM GPU or a PC GPU flashed with macEFI/EnableGop.

No, it is the stock HD 5960 inside.
I am definitely seeing the apple logo while booting into High Sierra, it is when I try to have access to Startup Manager I get the white screen with cursor.

 

[Zowan07]

Any other ideas...?