Configuring preferences and options in Outlook.com
I'm having the same issue, using a business mail account.
i've tried some troubleshootings in exchange admin panel, since i am an administrator, i could try to create another police to try some tricks, turning off and on the "Email Signature" feature in "Permissions -> Outlook Web App policies". Nothing new after that.
We just noticied that kind of situation in this week too in everyone who uses OWA in my corporation.
Editing bellow here
In time, something strange i noticed is that if i try to make a new email, no signature appears automatically(even if the options that set it up are enabled), if i try to force it by clicking in the 3 dots and trying to add it in "Add singarure", it keeps blank too and nothing happens.
But, if you go to settings and just see the signature configuration, even if you don't apply anything and then, try to make a new mail, it starts to show normally in a certain amount of time.
I wish it can help us all.
[]'s