You can receive one Ascendant Floret the first time, and only the first time you obtain any given Ascended Hero. After you summoned that Hero once, you cannot receive an Ascendant Floret when you summon the same Ascended Hero again.
Also, you cannot receive an Ascendant Floret when you obtain an Ascended Hero from a Combat Manual, regardless of whether or not you have obtained that Hero in the past.
If the above does not resolve your issue, please contact Customer Support via the Inquiries form at the bottom of the page and share the following information. If you share the below information with us when you contact us, our investigation will go more smoothly, so we request your cooperation.
1. The name of the Ascended Hero you got.
2. The approximate time and day you received the Hero in question (Please input this information in the Date and time section.)