Unable to upload an image

I get this error when trying to upload an image. "An error occurred in the upload. Please try again later."

My site was recently inaccessible and my host support has restored .htaccess

I had not modified anything. Perhaps this could be the fault?

They wrote "The problem you are facing is due to SEO friendly URL you have setup in your WordPress application but rewrite rules are not present in .htaccess file and I have checked that .htaccess file present in public_html directory is empty . "

Thanks in advance
Mark M.