I have updated the CA-Signed Device Certificate in a xerox 7845. The certificate is a PKCS12 bundle composed by private key, public key and CA chain certificate.
Key and certificate are accepted, but certificate is not chained with CA file so Firefox issues a warning: "unknown issuer".
How to upload a certificate whit CA chain?
In theory it should have linked it on the reboot.
Sadly there is no way to simply force it to do so though. You could try updating the firmware to the latest, and it would be a good try, but I don't think it will work honestly, but it is non-volatile and you won't lose anything.
Because after that things go from bad to worse.
The first step would be to wipe the device via Erase Customer data (Complete data loss will occur)
Machine status > Tools > Device Settings . General > Erase customer data > Erase customer data
At that point you would be setting it up from scratch. If it still fails the only thing left is the "nuke and pave" option
A technician performs an Altboot no data backup no clone to entirely wipe the device and reset every NVM.
And at this point you would be setting it up from scratch again.