Nerdio's wildcard SSL certificate (*.nerdio.net) has been renewed until 2021. RDP files generated by the Nerdio Admin Portal (NAP) are SSL signed. As a result, some users may receive an "Unknown publisher" warning when they click on their RDP shortcuts after 4/1/2019 (expiration date of the previous certificate).
It is perfectly safe to check the "Don't ask me again..." box and click Connect. This will prevent the warning from appearing again.
You may also choose to download a new RDP file from the Nerdio Admin Portal that is signed by the current SSL certificate. This can be done at https://app.nerdio.net or https://YourCompanyApp.adminportal.pro.
Clients can self-serve and get a new shortcut by using their normal logins at the above links.
If you log in as a Nerdio admin user, navigate to Users on the left and then click on "Generate RDP file" button to the right of the username.
If you log into the Nerdio Admin Portal as a regular user, simply click on the big "Get RDP login file" button in the middle of the screen.