Hi Kevin,
Apparently, this is the cause why I can't add an offline area in the new collector for iOS. However, I managed to download in the collector classic.
I am new in the company and there is no point to republish all the feature services, since surveyors and guys in the office have been using them for a while. I really want to move to new collector and I am willing to change all the field names which has listed values. Is there any clue to rename fields through ArcGIS Online ?
Thanks in advance