Graphics imported by reference not displaying after 2019 upgrade

We upgraded to FrameMaker 2019 from 2015 (unstructured). Now when we open our files, all of the anchored frames that we had imported gif files into at 133 dpi are not displaying the image. Only a dotted line where the referenced graphic should be displays. This did not occur with past upgrades. Did something change with the new version? Is there a simple solution to fix the issue?

Lynette Schwend