Export Import F5 Config 10.2.4 to 12.1.2

That is because the HTTP Class profile has been replaced by the Local Traffic Policies feature. See K14409: The HTTP Class profile is no longer available in BIG-IP 11.4.0 and later.

You need to edit the configuration file "bigip.conf" to remove the class profiles and any references to them and then try reloading the conf.