I have found the following information regarding ALM Synchronizer v12.55 being used with TFS 2017. Micro Focus advises that due to major changes in TFS, ALM Synchronizer can't support TFS 2017. You can click the link below to view the KM article regarding the workaround required to resolve the connection issue between your ALM Synchronizer and TFS 2017. The KM article contains a link that will download a word document with the steps for the workaround. I have posted the steps below that come from that workaround document. As far as the TFS 2017 support goes, Micro Focus advises that there currently is no way to work with TFS 2017, and anyone who wishes to use TFS 2017 will need to use the workaround to do so. TFS 2015 is the most recent version of TFS that is supported.
[ALM Synchronizer 12.55 - How to work with Team Foundation Server & Visual Studio v2017]
Steps to enable TFS and VSTS 2017 support?
Step 1: Navigate to C:Program FilesCommon FilesMicrosoft SharedTeam Foundation Server14.0 on the machine where Visual Studio 2015 is installed.
Copy all DLL files to C:Program FilesHPEHPE ALM Synchronizeradaptersnet2017 on the machine where the HPE ALM Synchronizer Server is installed.
Step 2: Register the TFS assembly file by running Register-TFS-Adapter.exe as Administrator in C:Program FilesHPEHPE ALM Synchronizeradaptersnet2017.
Step 3: Restart the Synchronizer server.
Step 4:When assign TFS endpoint connection properties you should input ServerURL in the following format:
http://:/tfs/DefaultCollection to connect to the default project collection.
http://:/tfs/ to connect non-default project collection.