Hey @hanhtran83,
I think you should try to refresh the window or log out and log back in.
It has happened to me with poor internet connection before so you should check that as well.
The last thing I can think of is the hashtags. I see your hashtags section is empty. That is, the section identical to the title section beneath the main body.
You should put some labels in small letters there which relate to the subject of your writing and separate them with a single space.
Eg.
You should be able to post after that.
As for the reduction in post rewards, it is absolutely normal. A lot of factors determine that value such as the current price of steem, sbd, curators activity, etc.
I invite you to take part in the newcomer's achievement program Lists of Achievement Tasks,Resources & Materials : Newcomers Resources so that you'll fully understand all of this.
Best wishes.
@njaywan: thank you for your reply. Now I can post my blog after adding hashtags at that square. The previous time, I added hashtags after finishing content by adding # at the end of the content. I have never added hashtags in that square.
If you post at any community, that community tag will be your first tag, for example tag for newcomers community is hive-172186, this tag will be your first tag, on the other hand if you post on your own blog, your first tag will be your primary/main tag.
@cryptokannon: yes. Thank you for your explanation. Now I can post my blog with my first tag.
Glad I could be of help.