We came across a situation when client was not responding back with the ACT data to ACT server.
To Workaround this issue you can follow the below steps:-
1. Go to the below location as per the ACT client OS.
For Windows 7 / Server 2008 / R2 –
%ProgramData%\Microsoft\Application Compatibility Toolkit\DataCollector
2. Go to the Failed folder where you will have cab files associated with inventory.
3. Copy these Cab files and paste it to root of ACT logs folder on ACT server.
4. Log processing service should automatically process these under processed folder.
5. Now you should see list of applications of those systems as well on ACM.
Hope this Helps!!!