WordPress no longer finds plugin directory

Hi,

I just noticed today that my authimage plugin wasn’t working correctly, (showing a broken/not found image). So I went to the word press admin plugins section and was told “Couldn’t open plugins directory or there are no plugins available”

They were working fine before! The only thing I could think I might have changed (a month ago) was to set up permalinks by creating the below .htaccess file. Would that have caused a problem?

Everything works fine (including the permalinks) except for plugins.

Thanks!
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RewriteEngine On
RewriteBase /workshop/
RewriteRule ^archives/category/(.*)/(feed|rdf|rss|rss2|atom)/?$ /workshop/wp-feed.php?category_name=$1&feed=$2 [QSA]
RewriteRule ^archives/category/?(.*) /workshop/index.php?category_name=$1 [QSA]
RewriteRule ^archives/author/(.*)/(feed|rdf|rss|rss2|atom)/?$ /workshop/wp-feed.php?author_name=$1&feed=$2 [QSA]
RewriteRule ^archives/author/?(.*) /workshop/index.php?author_name=$1 [QSA]
RewriteRule ^archives/([0-9]{4})?/?([0-9]{1,2})?/?([0-9]{1,2})?/?([_0-9a-z-]+)?/?([0-9]+)?/?$ /workshop/index.php?year=$1&monthnum=$2&day=$3&name=$4&page=$5 [QSA]
RewriteRule ^archives/([0-9]{4})/([0-9]{1,2})/([0-9]{1,2})/([_0-9a-z-]+)/(feed|rdf|rss|rss2|atom)/?$ /workshop/wp-feed.php?year=$1&monthnum=$2&day=$3&name=$4&feed=$5 [QSA]
RewriteRule ^archives/([0-9]{4})/([0-9]{1,2})/([0-9]{1,2})/([_0-9a-z-]+)/trackback/?$ /workshop/wp-trackback.php?year=$1&monthnum=$2&day=$3&name=$4 [QSA]
RewriteRule ^feed/?([_0-9a-z-]+)?/?$ /workshop/wp-feed.php?feed=$1 [QSA]
RewriteRule ^comments/feed/?([_0-9a-z-]+)?/?$ /workshop/wp-feed.php?feed=$1&withcomments=1 [QSA]