Answer
It starts with a finite set of trending suggestions. Search results load more as you scroll. Results already loaded stay in place if the next page fails; choose Retry. Clear search to return to the starting suggestions. Selecting a hashtag does not send your message.
If # is missing while @ai is on, check Chat Options → Advanced Options → Universal Hashtags. A default for the active type replaces manual selection; clear that type’s default to restore the picker. The scheduled composer follows the same rule.