Why didn’t you just get a new SOM, instead of replacing the IMX7 cpu?
https://www.technexion.com/products/system-on-modules/pico/pico-compute-modules/detail/PICOIMX7
Technexion’s installer can be found here:
Which points to:
Open up that *.zip archive and follow the pdf with the Installation Guide…
However since i don’t know how or with who you had the IMX7 replaced, there a chance it still won’t work. BGA’s are not trivial…
Regards,