Issue – domain.map file being ignored in Apache & nginx Settings

I am attempting to use a domain.map file full of redirects.
The location of the file is : /var/www/vhosts/system/MyDomain/conf/domain.map
I am putting the following into the Apache & Nginx settings :

RewriteEngine On
RewriteMap redirects txt:/var/www/vhosts/system/$MyDomain/conf/domain.map
RewriteCond ${redirects:/$1|NOT_FOUND} !NOT_FOUND
RewriteRule ^(.*)$ www.MyDomain${redirects:/$1} [R=301,L,NE]

The file is being read, because I can see it in lsof output
The file ownership and permissions are :
-rw-rw-r– 1 www-data www-data 1379486 Jun 17 21:02 domain.map

No errors appear to be generated in any log files I can find, including the ones in /var/log/apache2/error.log and /var/log/plesk-php??-fpm/error.log

I have tried temporarily disabling the Web Application Firewall

Grateful for any comments.