24135: Layer's pop-up definition includes date formats that are not supported online
You are sharing a web layer with one or more date formats defined in a pop-up that is not supported on ArcGIS Online. This can occur if you are using a custom configured date, such as hh:ss tt | MMMM, yyyy.
There are two situations that can cause this warning:
A date format is set for a field in the table that is visible in the Fields element of the pop-up.
A date format override is set in the pop-up configuration.
When multiple warnings are detected in a single layer, they are grouped into a single primary warning.
Solutions
Do one of the following:
Open the Configure Pop-ups pane for the layer and remove the date formatting for the noted field.
Open the Fields view for the table and remove the date formatting from the noted field.
Do nothing. The most similar supported format will be used.
Additional information
The same field can be configured to use differing date formats in both the attribute table and the pop-up. For more information about formatting a date field in ArcGIS Pro, see Format numeric and date fields. Alternatively, see Configure pop-ups for information regarding ArcGIS Online pop-ups.