Usually this alert is shown upon opening P&ID export copy that was imported to project. In this case this alert informs that P&ID does not have any intelligent data. In cases when this alert is received upon opening P&ID model that was not imported, the following workflow could be used in order to resolve this issue. 

1. Open P&ID model in vanilla AutoCAD
2. Erase _AT_EXPORTCOPY block from model. In order to locate block use QSELECT or Object Selection Filters.
3. Purge model and make sure  that block no longer exist.