Hi @Debby ,
You are right, PDF is not controlled by Microsoft, maybe Microsoft has changed the security policy, affecting the compatibility of the two. But I don't know the specific details. If you want to know, you can go and find higher level support.(Microsoft 365 admin center ->> Support ->> Help & support)
Alternatively, you can also go to Feedback this issue, this is the best platform to let us hear from you and make our products and services better for you and others. Microsoft values its customer feedback and a lot of features have been developed and suggested by customers via feedback. Your feedback is also very important.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.