For internal catalog, Please provide the screenshot of the screen before it becomes blank.
For Punchout catalog:
- First check Catalog view is properly maintained in the WEB SERVICES in SPRO settings.
IMG->SAP SRM->SRM Server->Master Data->Content Management->Define External Web Services.
- Check the same Catalog view Id is assigned to the user.
- Is the blank screen appearing for any particular product or Is it happening for all the products of that catalog? Ask for OCI parameters from Cloud/ MDM team and check if there is any special character in it which is not supportable in your SRM system.