I have seen this issue a couple of times and decided to blog about the solution …. The problem is that Unified Service Desk fails to load.
The symptoms of this problem are that Unified Service Desk starts to load but then suddenly dies. No error message is given (at least not visibly). There is however an error reported in log files.
To find you log files navigate to “%appdata%” in file explorer. This will take you to a folder called something like “Users/<<Your name>>/AppData/Roaming”. Then open the “Microsoft” folder. And within that “Microsoft Dynamics 365 Unified Service Desk”. Finally you will find a directory which is the version of USD client you are using. I am currently using “126.96.36.1993”. Once in this folder you will find some text files. Opening the most recent will show you a log of any issues.
I have shown the required folder path and text file below;
Opening the text file with something like NotePad will allow you to review any errors. If you have the same issue as me then towards the end of this text file you will see an error complaining about multiple tokens. In my example this was actually caused by me repeatedly swapping from one user login to another. Something most end users won’t routinely do but when developing / testing I do tend to jump from instance to instance and therefore user to user. I have shown the end of my log file below, so that you can confirm your error message looks similar.
The text of the error message is “multiple_matching_tokens_detected: The cache contains multiple tokens satisfying the requirements. Call AcquireToken again providing more requirements (e.g. UserId)“.
Ok, so you have found that USD is crashing and checked the log files to confirm you have an issue with multiple matching tokens. How do you fix it? Luckily the answer is easy!
Firstly look in a different folder. You are still looking for a folder in “%appdata%/Microsoft”. But this time it is called “USD”. In here you will find a file call “Default_USD.tokens.dat”. You simply need to delete this file try loading USD again.
If you have issues with USD loading hopefully this fix might be helpful.