is this string correct?
Download+Export+File+?&addquicktag_download=true
especially the ?&
Yes, absolutely correct.
Frank, in a similar way the line looks in the Safari.
In the Opera, Firefox and Chrome the address looks a little differently →
wp-admin/options-general.php?_wpnonce=c05b6ffb9d&_wp_http_referer=%2Fwp-admin%2Foptions-general.php%3Fpage%3Daddquicktag%2Finc%2Fclass-settings.php&submit=Download+Export+File+%C2%BB&addquicktag_download=true
However export is impossible IN ALL listed browsers: I see the same message.
Has noticed still that the address from options of a plug-in changes a little if to click the link “Please try again”.
The address of options of a plug-in as I already wrote, such →
wp-admin/options-general.php?page=addquicktag/inc/class-settings.php
After unsuccessful attempt of export and returning to page of options, the address looks so →
wp-admin/options-general.php?page=addquicktag%2Finc%2Fclass-settings.php
I hope, it somehow will help you, dear Frank..