Chrome on MacOS started rejecting self-signed certificates Starting 4 days ago (the date might be relevant if some updates came along),
Chrome on MacOS started rejecting self-signed certificates. It includes things like Vagrant boxes and the Synology NAS web interface. 

While with Chrome under Windows I can still click "advanced" and chose to "accept the risk and continue", that option is missing under Mac.

Is there any Flag or Setting to reintroduce that option?
Try to run the following command from the terminal and relaunch Chrome

defaults write com.google.Chrome EnableCommonNameFallbackForLocalAnchors -bool true


This can help you to solve your issue. 

Or 

If you need a workaround to get the site working without replacing the certificate you can do the following.


Download the certificate from the server (using another browser or with openssl)
Install the certificate into Keychain Access under the login store
Set the certificate to "always trust" by double clicking on it once it's been installed.