Basically what is happening is that you probably have core oxwall images that are being loaded http because that is how they are assigned in css or that is how they are written in the newsfeed and other tables.  Or youttube videos are being loaded by https but the associated image is being loaded http.

Have you tried forcing https for everything that is loaded?

Did you change the ow_includes/config.php file to https?

See the last post here (untested)

https://developers.oxwall.com/forum/topic/45671

You can also see here 

https://developers.oxwall.com/forum/topic/63622

Here is the resolve shared by the user.  

i contacted a2hosting and they asked me to add below code in .htaccess file and i did it and now showing secured. 

<IfModule mod_headers.c>

 Header always set Content-Security-Policy "upgrade-insecure-requests;"

</IfModule>

This worked for the OP and they shared it with me.  So im posting it as a possible solution.