Have you enabled the server in PHD2?
PHD2 Server
PHD2 supports third-party imaging and automation applications that need to control the guiding process. Sequence Generator Pro is probably the most popular of these but there are numerous others. By using the PHD2 server process, image capture programs can control dithering between exposures or suspend guide exposures while the primary imaging camera is downloading data. To use these capabilities with a compatible application, you should click on the 'Enable Server' option under the 'Tools' menu. The PHD2 server interface is quite extensive, and it's possible for an application to control most aspects of PHD2's guiding operations. Documentation for the server API is available on the PHD2 Wiki.
https://openphdguiding.org/man-dev/Tools.htm