Big Sur - will not boot with Thunderbolt monitor connected

I have a MacBook Pro 15" mid-2014

with Nvidia GeForce GT750

Intel Iris Pro 1536 MB

Upgraded from Catalina to Big Sur.

Install appeared to succeed.

However, the computer hangs at initial boot up whenever I connect my external Apple Thunderbolt Monitor.

System will boot without the Thunderbolt monitor and then successfully connect to Thunderbolt at boot up.

Unfortunately, this keeps my MBP from using the Thunderbolt monitor with my Win 10 Bootcamp since Windows will not recognize the monitor unless connected at initial boot up.

I have reset SMC to no effect.

Rolled back to Catalina thru TimeMachine backup to no effect.

Performed clean install of Big Sur by external USB which succeeds but does not fix boot with Thunderbolt issue.

Any ideas on a cure?

Thanks.

MacBook Pro 15″, macOS 11.0

Posted on Nov 14, 2020 6:55 PM

Top-ranking reply

etienne68yellow

Level 1

18 points

Posted on Dec 15, 2020 11:29 AM

ALL SORTED...

I spent hours on the phone with Apple Ireland about this issue last week and they remotely took over my Macbook Pro and did loads of unfathomable tech stuff as I watched, including taking time-stamps of actions they did, as they occurred in real time.

They rang me to let me know that they were about to release macOS Big Sur 11.1 and that the engineers had inserted some coding to hopefully sort my/your issue.

They rang again tonight and asked me to download, install and restart to test it, and they waited while the install occurred etc.

And it works.... Macbook now happily reboots with Thunderbolt monitor attached, etc

Happy Christmas one and all.

Giles

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Big Sur - will not boot with Thunderbolt monitor connected

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