Hi Masa,
Thanks for your collaboration see below.
1. Test it on iPhone same issue (no HTML description is displayed)
2. Use Chrome browser on iPad. Same issue
3. Set external breakpoints in your BADI Implementation. OK
If the BADI is not called, some configuration is related. NA
If the BADI is called and additional HTML description is available, YES check the OData response.
If the HTML description is missing, further debug is required. BADI is called and HTML description is there see attached documents for ODATA service results
Regards.
Rachid.