Cs-Cart Multi Vendor Edition Setup With Lets Encrypt Issue.

(I am new to cs-cart and trying to set up cs cart multi-vendor edition) Everything worked fine before installing ssl certificate. After installing Load-Balance server with lets encrypt SSL certificate which also terminates SSL and redirects any incoming request on port 80 to 443. Response to www.example.com partially displayed the site (looks like site without css) and also displayed popup notification saying some or partially website accessed using http where certificate information icon located. My question, what causes site to display partially, some links not accessible. Is there anything that I need to change such as conf files.

Here is my setup

Load Balance server : Ubuntu 20.04 with NginX installed. Using layer 7 proxy pass to upstream servers. Listening on port 443 redirects any incoming port 80 to 443

Web server 1 : Ubuntu 20.04 with Apache2 as webser1 listening on port 80.

Web server 2 : Ubuntu 20.04 with Apache2 as webser2 listening on port 80.