I am not sure letsencrypt certificate is working?

[zeus]

In some cases it might happen. Clear your browser cache and then reload. Or, try a different browser.

If your site is loading in https version then the certificate is alright.

I agree. I don't think SSL are going to mess with the site's templates. Rather it will load or not.

And to OP I say, generate a new certificate if you have doubt that this is messed up.