Try this! Worked for me same issue!
I was in the same boat. For anyone having this issue, you cannot just connect to Wi-Fi, you have to actually get an active SIM to connect to the network. I went and purchased one online from one of those international carriers for about five dollars and as soon as it got a data connection within five minutes I had the OEM unlocking option available. Before I was just on Wi-Fi I did not have that option available to me. You have to have an active eSIM or a regular SIM on the phone and it has to connect to data.

TLDR - Had the same issue with an Amazon phone as soon as I got a data-only eSIM and it connected within five minutes OEM unlocking was available to me. Wi-Fi only did not fix the problem.

  • tmp replied to this.

    Oh wow, my OEM unlocking randomly enabled today! Took about 24 hours of being online for some reason. Seems we just need to be patient. I literally did nothing special, just been using the phone normally.

    entreri There were no issues when the Pixel 6 came out. There were only issues with the Pixel 6a which were resolved by updating to the first over-the-air update and doing a factory reset. That has never happened with any device other than the Pixel 6a and was only an issue with the release initially shipping with the early batches of devices. It was resolved in the first update available on launch day as an over-the-air update, but the fix didn't retroactively resolve it deciding it wasn't an unlocked device.

        GrapheneOS Thanks for the clarification. No worries it finally enabled for me. Just had to be patient and wait 24 hours. Time to install GrapheneOS!

            @[deleted] What is posting this elsewhere supposed to accomplish?

            I definitely didn't like the vibes over on the GOS forums. They are being rather obstinate and harsh in listening to anything we have to say regarding this, saying there zero possibility it's anything other than us not getting unlocked phones, despite a similar situation to this happening with the launch of the 6a as well.

            This is nothing like the Pixel 6a issue which was a bug in the factory installed OS release which was fixed before launch and available in the day one update, but the fix didn't retroactively resolve that it decided it was a carrier locked device. That's not like this at all where most people didn't have issues unlocking but rather it appears that some devices which were sold were not entered as unlocked into the database.

            entreri It's likely there was a delay entering devices into the database since there appears to be no OS issue and the warranty/repair/unlocking service is working fine overall. Seems some devices were not entered into it or were wrongly entered into it as locked. It doesn't sound at all like a bug but rather a delay in the process that's supposed to happen. Perhaps Google didn't mark some batches of devices sold via Amazon and Best Buy as unlocked or processing it was delayed for some reason. It sounds a lot like they noticed the complaints and dealt with it.

                Hello all, after reading the messages here and on Reddit I decided to reboot my phone. "OEM unlocking" no longer disabled! Best of luck and I appreciate everything the GrapheneOS developers and community has done.

                  Compuboy04

                  Just finished an alpine cli install on an 8a purchased from a local best buy. net connectivity via wi-fi only, no sim, no issues.

                    My Best Buy sourced phone is fixed now. OEM Unlocking is now enabled.

                    • de0u replied to this.

                      GrapheneOS this sounds like the most plausible explanation. Thanks for your replies.

                        4 months later

                        de0u My Pixel 9, no matter what I did the dreaded OEM wont allow me to toggle for whole day. Did the checkin and reset the device, now working, thank you!!

                        • de0u replied to this.