I have configured a SSL certificate in azure, this is how the configuration pages look.
But when I navigate to the site I get an 'your connection is not secure' error, looks like no certificate exists.
An Chrome on the other hand it looks invalid
You can verify if you have added binding with your custom hostname which should map your SSL certificate DNS name in your Azure Web app service.
This isn't an Azure issue, its a fault with your cert. Your certificate shows as using the "Fake LE Intermediate X1" intermediate cert. This is usually down to using the let's encrypt test/staging service which does not issue valid trusted certs. Make sure whatever process you are using to generate the cert is using the production LE servers.
I've ended up purchasing a new certificate from azure and gave up on trying to integrate let's encrypt.