The following warning message appears when migrating a subscription:
CONFIG_TEXT: The PHP handler 5.5 FPM application (id=fpm) is not available on the destination server.
Instead, Plesk will use the following PHP handler: 5.5.38 FPM application served by Apache (id=plesk-php55-fpm)
The PHP version installed on the source server is not installed on the target server, that's why Plesk Migrator suggests using another installed PHP version.
This warning message can be safely ignored.
In case it's required to keep using the same PHP version, install it on the target server following the steps described here: How to install Plesk components?