At some point during my use of ArcGIS Pro 2.3, I confront with this image. It comes when I have tried to open a data table from a feature class that's in my project. My feature classes link to a SQL Server table that's immutable. Anyway, is the issue that my data linkages are unindexed?
The ole' turning it back off and back on again (restarting ArcGIS pro) seems to fix the issue at least temporarily.