In order to use Totango-tab when a custom-domain is used in Salesforce, you need to configure the Totango URL as one of the trusted IPs. Follow these 2 steps to configure it:
1. Go to set-up -> Security Controls -> Network Access
add new entity:
Enter Please enter the Totango IP list both as start and end addresses.
Please follow the instructions in this Customer Data Hub IP Whitelisting article to configure your IP whitelist.
2. Go to Manage Apps - > Connected Apps -> TotangoApp
Click on "View OAuth Usage" to get to "Connected Apps OAuth Usage", find "Totango Gateway" entry and install it.
In order to verify a successful installation, go to the"Connected Apps OAuth Usage" page, and verify that the "Totango Gateway" is installed and unblock (it should look like the image below)
The setting should apply after a couple of minutes and the tab should be loaded successfully,
If you encounter further issues please contact firstname.lastname@example.org