Issues with OSD in secondary MCM 2509 site

Hi, having upgraded primary and secondary MCM site to version 2509 I cannot perform OSD anymore on secondary site location - errors:

Failed to query Management Point locator

QueryMPLocator: no valid MP locations are received

Boundary Group in secondary site does have assigned MP and that is secondary MCM site server - however I get this as well:

<MPLocation SiteCode="" AssignedSiteCode="" MP="" MPCertificatesEx="" x86UnknownMachineGUID="" x64UnknownMachineGUID=""/>

Any help would be highly appreciated.