Ganttman Pro not connected

I have a license for Gantman Pro. I have installed the APP on the new Android mobile, but when I try to connect open the DropBox icon I get a message AN ERROR HAS OCCURED. ARE YOU CONNECTED? I have installed DropBox App, and I can see files. I have tried with Wi-Fi connection & mobile data connection. Any idea?

You’re writing to the wrong chat. Please address your question to the developer(s) of Ganttman Pro. We have no affiliation with them.