Issue Site without PhysicalHosting cannot be Webspace

[burnley]

Recently when we deploy URL forwarding service from our billing system plesk has been spitting out the error" Site without PhysicalHosting cannot be Webspace" although client and subscription are actually deployed in Plesk. However the error results in order remaining in pending state. We have been using the same service plan etc for many years so something is changed but we can't isolate it. Can anyone on the forum or plesk give me some ideas what has changed or needs to be changed to get it working again please.

We have "Enable hosting=off" in the service plan as physical host / ftp user etc isn't required for a URL forwarding service. Below is the API call example and response.

PleskAPI: host.domain.tld:8443@addSubscription_WithUrlForwardingRequest:
<?xml version="1.0" encoding="UTF-8"?>
<packet>
<webspace>
<add>
<gen_setup>
<name>example.com</name>
<ip_address>123.123.123.123</ip_address>
<owner-login>aglag8iiauvfqog</owner-login>
</gen_setup>
<hosting>
<frm_fwd>
<dest_url>target.tld/example/</dest_url>
<ip_address>123.123.123.123</ip_address>
</frm_fwd>
</hosting>
<plan-name>DNS / URL Forwarding</plan-name>
</add>
</webspace>
</packet>

Response:

<?xml version="1.0" encoding="UTF-8"?>
<packet version="1.6.9.1">
<webspace>
<add>
<result>
<status>ok</status>
<id>4332</id>
<guid>78c333cc-6865-41dd-b4a0-0904f84cf826</guid>
</result>
</add>
</webspace>
</packet>
Server:host.domain.tld:8443

Which works fine but then gets stuck when it tries to sync the subscription to the service plan;

PleskAPI: host.domain.tld:8443@syncSubscription_WithServicePlanRequest:
<?xml version="1.0" encoding="UTF-8"?>
<packet>
<webspace>
<sync-subscription>
<filter>
<guid>78c333cc-6865-41dd-b4a0-0904f84cf826</guid>
</filter>
</sync-subscription>
</webspace>
</packet>

Response:

<?xml version="1.0" encoding="UTF-8"?>
<packet version="1.6.9.1">
<webspace>
<sync-subscription>
<result>
<status>error</status>
<errcode>1023</errcode>
<errtext>The plan was not applied because of problems with the following functionality: Site without PhysicalHosting cannot be Webspace</errtext>
<filter-id>78c333cc-6865-41dd-b4a0-0904f84cf826</filter-id>
<id>4332</id>
</result>
</sync-subscription>
</webspace>
</packet>
Server:host.domain.tld:8443

The service plan has 'Enable hosting=off' as physical hosting e.g. ftp user and databases etc are not required.