I know I just arrived and I am necroposting already, but this is exactly what has happened to me when trying to download the 2022 maps.
When I try to do it through the Lexus tech website, all goes fine exactly like the OP described. Downloaded the maps to a proper formatted FAT32 32GB pen drive, started the install with no issues, and then the error message "IE5585-Not able to determine product mapped to SKUID" appeared right after putting down the request code from the sat nav screen on the Lexus tech website.
I also have the final activation code from purchasing the 2022 maps (in all fairness didn't pay, the dealer included as a token to buy an approved used), and that activation code also doesn't work when putting it in after the request code.
To sum up, after putting the device ID correctly on Lexus tech website, then putting the request ID from the satnav, and the error appears. But if I go ahead and put the activation code that I was given when purchasing the map in My Lexus, a different error appears: 'unable to validate the code' or similar. So no way around it.
If anybody has any ideas, I'd greatly appreciate it. Tried everything. I just contacted technical support of Lexus through the contact form, hope they get back to me. The dealership is aware of the problems, they said they opened a case with Lexus UK, but no contact after a week. I understand they can be busy, but I thought there's no harm in asking here.