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CloseReview for Thunderbird Conversations by MorpheusUK
Rated 4 out of 5 stars
I am seeing the same issue in TB 91.1.1 as Tony on Sept. 21, 2021 https://addons.thunderbird.net/en-GB/thunderbird/addon/gmail-conversation-view/reviews/1167942/
I selectively disabled the display affecting add-ons until i had narrowed it down to this one. This is with version 3.2.34.
Update:
Disabling all add-on then first re-enabling this one followed by the rest has it working again.
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