Disappearing message enabled by mistake
Open Messenger on your phone.
Open the conversation where messages are disappearing.
Tap the person's name at the top of the conversation.
Look for Disappearing messages.
Tap it.
Select Off (or Never, depending on the version of Messenger).
Important:
Turning it off does not necessarily bring back messages that have already disappeared.

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Facebook Messenger
Video call error with Messenger:
An Error occured when trying to get access to Microphone Access to Media Devices has been denied
or
Hardware Access Error
Windows 10 parameters
Check "Privacy":
"Microphone" set "Allow apps to access your microphone" to ON
"Camera" set to ON
and
Google Chrome or other internet browser:
Check the Privacy Settings to authorise access:
Chrome > Settings > Privacy and Security > Site settings > Microphone
Chrome > Settings > Privacy and Security > Site settings > Camera
and/or
Ckeck with webcam_test
if error check with webcam software e.g. Logitech C920 Pro webcam: Capture application