We are sorry for the trouble. As described, all the online documents have become restricted and you are not able to fill and sign.
Would you mind sharing the steps you are doing to fill and sign the PDF file?
Do you get any error message when you try to fill and sign the PDF? if yes, please share the screenshot of the same for a better understanding. Also, please share the file with us for testing.
IF the file is stored on a shared network/drive, please try to download the file...