Go to the page linked in the message: Your flags (only viewable to you and mods). This is the same page that the "Helpful Flags" link on the "Activity" tab of your profile page goes to.
There is no button, or anything like in the review queue. All SE wants you to do is read the message under the flag(s) in question, and make sure you understand why your flag was declined.
You still can flag posts (it says so on your flags page).
- Not banned from flagging
- Warned when flagging
You can read the details about how the flag warning and banning system works here: https://meta.stackexchange.com/a/175405/278094.
If you flag more then 10 flags per week you will get warned when more then 10% are declined, and temporarily banned if more then 25% are declined.
If you have less then 10 per week (this is your case at the moment) you will get warned if your last flag was declined.