Cannot upload to a shared OneDrive folder

I have a Microsoft 365 personal account. I have shared folders for the recipient to upload files too. The recipient has been able to upload in the past with no issues; however the last couple of months they can no longer upload files to my shared folder. They have full edit permissions; they can access the folder, they can download files from the folder but they cannot upload to the folder. They receive no error messages just a blank screen. They have tried dragging and dropping the files, it looks like it will upload but then nothing happens, same occurs if they click the option to upload file or folder lets them select the file and click upload but again nothing happens. Folder remains empty and there are no error messages or pop-ups received. I have deleted the folder and created a new one; shared via a link and via an email address same issue. I have shared folders with other recipients to see if the issue is isolated to one person; it is not it happens to all from different folders created and shared. Not sure what has changed as I have been sharing folders for over 3 years for the recipient to upload with no problems. What has changed and how do I fix this?