.htaccess not writable

When I submit my changes in the settings tab in this plugin, I receive a pop up saying that I manually need to modify my .htacccess file with the following code in order to save my options:

# BEGIN WpFastestCache
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
AddDefaultCharset UTF-8
RewriteCond %{HTTP_HOST} ^www.seminarreview.com [NC]
RewriteRule ^(.*)$ http\:\/\/seminarreview\.com\/$1 [R=301,L]
RewriteCond %{REQUEST_METHOD} !POST
RewriteCond %{QUERY_STRING} !.+
RewriteCond %{HTTP:Cookie} !^.*(comment_author_|wordpress_logged_in|wp-postpass_|wp_woocommerce_session).*$
RewriteCond %{HTTP:X-Wap-Profile} !^[a-z0-9\”]+ [NC]
RewriteCond %{HTTP:Profile} !^[a-z0-9\”]+ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(iphone|midp|sony|symbos|nokia|samsung|mobile|epoc|ericsson|panasonic|philips|sanyo|sharp|sie-|portalmmm|blazer|avantgo|danger|palm|series60|palmsource|pocketpc|android|blackberry|playbook|ipad|ipod|iemobile|palmos|webos|googlebot-mobile|bb10|xoom|p160u|nexus|touch|SCH-I800|opera\smini|SM-G900R4|LG-|HTC).*$ [NC]
RewriteCond %{DOCUMENT_ROOT}/wp-content/cache/all/$1/index.html -f [or]
RewriteCond /var/www/sites/seminarreview.com/wp-content/cache/all/$1/index.html -f
RewriteRule ^(.*) “/wp-content/cache/all/$1/index.html” [L]
</IfModule>
<FilesMatch “\.(html|htm)$”>
FileETag None
<ifModule mod_headers.c>
Header unset ETag
Header set Cache-Control “max-age=0, no-cache, no-store, must-revalidate”
Header set Pragma “no-cache”
Header set Expires “Mon, 29 Oct 1923 20:30:00 GMT”
</ifModule>
</FilesMatch>
# END WpFastestCache
# BEGIN GzipWpFastestCache
<IfModule mod_deflate.c>
AddType x-font/woff .woff
AddOutputFilterByType DEFLATE image/svg+xml
AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/html
AddOutputFilterByType DEFLATE text/xml
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE text/javascript
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/javascript
AddOutputFilterByType DEFLATE application/x-javascript
AddOutputFilterByType DEFLATE application/x-font-ttf
AddOutputFilterByType DEFLATE application/vnd.ms-fontobject
AddOutputFilterByType DEFLATE font/opentype font/ttf font/eot font/otf
</IfModule>
# END GzipWpFastestCache
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

I went ahead and modified and updated my .htaccess file, but I am still getting the pop up. I’ve tried deactivating and then activating the plugin as well as reverting back to my original .htaccess file and then modifying again, but nothing is working.

Is there another step that I’m missing or is there something wrong with any of the rules that are written above?

https://wordpress.org/plugins/wp-fastest-cache/