Salesforce Mobile App Issues - Lightning Components, My Domain Settings, Clickjack Protection

Having certain features turned on can have a negative impact on the Salesforce mobile app. The following are a few settings to check if the app is not behaving as expected.

Do you have Lightning Components enabled?
This frequently causes problems for our customers. To confirm and deactivate it, navigate to the Lightning Components page in in Setup (under Develop in Classic interface, or Customize in Lightning interface). Uncheck the Enable Lightning Components box and Save.

Are you using a custom domain?
If you are a using a customized domain to access Salesforce, you'll want to make sure the domain is set up correctly. Navigate to the My Domain page in Setup (under Domain Management in Classic or Company Settings in Lightning). If enabled, make sure your Redirect policy is set to 
Redirect users to the same page within the domain.

Do you have Clickjack protection enabled?
Your sessions settings could also be a problem. Navigate to Session Settings in Setup (under Security Controls in Classic or Security in Lightning). In the Clickjack Protection section, uncheck these options:

Enable clickjack protection for customer Visualforce pages with standard headers
Enable clickjack protection for customer Visualforce pages with headers disabled

If you continue to have problems after changing each of these settings, please let us know.