With the recent release of Portal 2.44 - aka Qualys Cloud Platform 2.44 - a change was made to limit the size of web application reports.
A notification will be displayed if you try to create a web application report having 100 to 500 web apps. With this number of apps, you have an option to download the report in your desired format (PDF, HTML, CSV, etc.):
If you try to create a web application report having more than 500 web apps, you'll get an error message stating the report cannot be generated:
As mentioned in the release notes, this change was made to prevent recurring failures in creating very large reports. Creating such reports in many cases would either fail completely after some time or take an extremely long time to finish (many hours). This was frustrating to customers. Furthermore, it was observed that generation of very large web app reports by one customer would lead to resource contention on the shared platform infrastructure and negatively impact report generation for other customers.
Therefore, the limit was imposed to enhance stability and reliability of the platform to the benefit of all WAS customers. The new limitation will affect relatively few customers, but if you are an affected customer, please reach out to your Technical Account Manager (TAM). There are different options available in terms of retrieving scan results, such as leveraging the WAS API. Qualys has subject matter experts (SMEs) available to consult with you to offer alternatives to help meet your particular business use-case.
It's also recommended to review the Qualys Reporting Best Practices FAQ for general tips and guidance with it comes to reporting within Qualys.