I cannot download and open gmail attachments.
What email client are you using, or are you using a web based email?
Has this just started happening, or has it been going on for a long time?
Do you have a VPN active when this happens? Are you able to access your attachments with the VPN off?
I am using gmail and this started yesterday when I installed Norton, no VPN. I noticed a few minutes ago that it works when I use the Norton browser but not MS Edge.
What security software did you have before installing Norton? Did you fully remove that using the removal utility for that software before installing Norton?
All I used was Defender and when I look now it is controlled by Norton.
As a test, go into 360’s Settings and disable the Safe Web feature and test. From the 360 interface, click on Settings in the left pane, then click on Safe Web from the Features tab. Then turn off Safe Web and test.
I found an old security package that I had forgotten when I delete it things worked. Thank you for your help.
Good news. Thanks for posting back.
We install and uninstall so many things on our systems it can be easy to forget everything we have used.