I migrated one customer from Dynamics CRM 2011 On-Premise to D365 Online and everything was fine until customer discovered that account form looks weird – one section just disappeared:
And here is how the same section looked like in “Customization” mode:
So controls were there but something just made it invisible. After some investigation my manager Paul Way realized that “Bing Map” control is the root of this issue. It works the following way – when in “System Settings” native integration with BingMaps is turned off – Bing Maps control (if it is on the form) hides not only the control itself but the whole section it belongs to. So the solution was straight forward – either to remove the control from the form or put it to separated section, save and publish changes. After it issue disappeared and section and fields on it were visible again.