Thanks for writing in PI Square !
Please let me me know which version of Notifications you are using and if this issue was happening before.
There are several things that could be happening in your system to show "No Data".
First of all I would like you to have a look to the following KB article: KB01135 - PI Notifications email says "No Data" for some attributes
Please also check if the data type from your AF attribute and the one from your PI Point matches. I have seen issues when the AF attribute was selected as a string and the PI Point was a float.
Let me know if you need further help,