Web part should be loaded.
Error details: Error: *Error initializing application. Error: Error: *Error initializing application. Error: TypeError: Cannot read property 'groupColor' of undefined
Follow all steps from https://docs.microsoft.com/en-us/sharepoint/dev/spfx/web-parts/get-started/using-web-part-as-ms-teams-tab
"Notice how you can parametrize the tab instance based on the exposed properties. Click Save". You won't notice that because of bug with initialization.

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Same here - different tenants but the same error. Unfortunately I'm about to demonstrate this on a conference tomorrow - worst timing for this error ;-)
@VesaJuvonen is this because of changes with SPFx 1.8 coming?
That's really unfortunate timing and yes - this is related most likely on the 1.8 release, but investigating exact details internally. TBH - I doubt that the situation will be changed by tomorrow.
I experienced the same yesterday during the day, but it got fixed.
This should have been now fully fixed after the 1.8 deployment. It was a version conflict before go-live. Can we confirm that we are good? Thx.
@VesaJuvonen I will check and let you know. Thank you very much.
@VesaJuvonen wow. It is working even better. Thank you very much, closing this issue.
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That's really unfortunate timing and yes - this is related most likely on the 1.8 release, but investigating exact details internally. TBH - I doubt that the situation will be changed by tomorrow.