Gzip compression not working though MOD_DEFLATE is On

I am trying to enable GZIP compression, but I kept encountering error message saying

"gzip is not working properly:
- Your server may not have the "deflate" module enabled (mod_deflate for Apache, ngx_http_gzip_module for NGINX)
- Another plugin may be interfering with the configuration
If re-checking and restarting does not resolve, please check with your host or open a support ticket with us."

I've tried doing this manually editing .htaccess using the code supplied. That doesn't work. I've used a similar code supplied by my hosting provider and this has resulted in text/html being enabled, but not text/javascript or text/css.

I've checked the providers code to ensure javascript and css are included as lines e.g.
" AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE text/javascript "

But to no success. I've rather reached the limit of my knowledge here. Any suggestions?

Thanks!