Identity Manager 14.1 CP3
Customer had originally built a custom UI for their customer and during migration they brought the UI over.
The issue stems from not having access to the base path for UIs customer had to place the UI in the imcss folder.
The relative pathing to access this UI is as follows: ".../identityEnv/imcss/TFGUI/" unlike the default "ui7" that sits in ".../identityEnv/ui7/"
We found that users browsers have cached data from the old Environment.
This interfered with the pathing resulting in the failure described above.
Users had to clear their history and restart browsers. This resolved the issue.