Facebook messenger won't let me unmute a conversation! HELP PLEASE?

NNM19
I muted a conversation I had in Facebook messenger with the option "until I turn it back on" and I have turned the conversation back on several times but a little message still keeps saying "notifications for this conversation are of. Turn on?" I keep turning the conversation on but the message keeps popping up. How can I turn my notifications for this conversation back on?

Facebook keeps muting it on its own
Facebook messenger won't let me unmute a conversation! HELP PLEASE?
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