I set "Yes" for both "Use Secure URLs on Storefront & Admin" in backend.
After saved, the site still in "information or insecurity" mode, and
the frontend not in normal displaying,
and get "ERR_TOO_MANY_REDIRECTS" message from admin page.
Just remove var/generation, var/page_cache and var/view_preprocessed folder from root.
Give full permission to var generation folder and pub/static folder.
Run below command,
php bin/magento setup:upgrade php bin/magento setup:static-content:deploy php bin/magento cache:flush
Clear browser cache.
have you check your mod_rewrite is enable or not? If not enable please enable mod_rewrite.
if issue solved,Click Kudos/Accept as solutions.