Cant Upload RDL File to SSRS 2016

I've wasted half a day trying to figure out a solution for this issue.

We just stood up a SSRS 2016 server. Everything looks great. We're able to access the site with the URL we created. I can set the permissions and create folders.

However, when I wanted to test out a simple RDL file, which only has a text box, it fails to upload. I get the famous "an error has occurred. Something went wrong. Please try again later."

Just for giggles, I uploaded a simple image file and boom, it uploaded just fine. NO errors whatsoever. But when I go back and try to upload an RDL file, that's when I get the error.

The way I'm trying to upload the RDL file is by going to the web portal and then clicking on the big UPLOAD button. Then I browse to my file and then Open to start the upload. Again, error appears. Not only can I not upload an RDL file, but I cant even create a new Data Source from the web portal. I get the same error. Permissions is not an issue since I'm using an admin account.

Like I said, I've been searching and searching but nothing.

Hoping someone here has experienced this issue and resolved it.

Thanks guys!

Just a guess
Try to open the browser as administrator and try again.