Since UVC 6.8.21 it's not possible to create or update an Alerting Rule with a plus sign (+) in the Label .
This was possible in previous versions.
This problem was introduced by a fix in "Alert rule" menu done in UVC version 6.8.21.
Since that version, the allowed characters do not include the sign "+" anymore: only A-Z0-9_-.()@#$ are accepted
It is now possible to create or update an alerting rule with the following authorized characters A-Z0-9_-.()@#$+
Update to a fix version listed below or a newer version if available.
Fix version: Dollar Universe 6.9.61
Release Date: 15th January 2019