Connection Db - Help

Help help, I was doing my software when I wanted to enable the experimental features and maybe I changed something about the db connection … it turns out that all the connections don’t work … I disabled the experimental functions again but the db connections don’t work anyway. please give me a hand
wappler 3.5.7
win 10
remote mysql php server
I report the error that all queries give

{“code”: 0, “file”: “\ / home \ / phonerec \ /app.phone-recovery.it \ / dmxConnectLib \ / lib \ / db \ /Connection.php”, “line”: 36, " message “:” Connection String is Required “,” trace “:” # 0 \ / home \ / phonerec \ /app.phone-recovery.it \ / dmxConnectLib \ / modules \ /dbconnector.php (12): lib \ db \ Connection -> __ construct (Object (lib \ App), Object (stdClass), ‘test_conn’) \ n # 1 \ / home \ / phonerec \ /app.phone-recovery.it \ / dmxConnectLib \ / lib \ /App.php (193): modules \ dbconnector-> connect (Object (stdClass), ‘test_conn’) \ n # 2 \ / home \ / phonerec \ /app.phone-recovery.it \ / dmxConnectLib \ / lib \ /App.php (127): lib \ App-> execSteps (Object (stdClass)) \ n # 3 \ / home \ / phonerec \ /app.phone-recovery.it \ / dmxConnectLib \ / lib \ / App.php (92): lib \ App-> exec (Object (stdClass), true) \ n # 4 \ / home \ / phonerec \ /app.phone-recovery.it \ / dmxConnect \ / api \ / vers_2 \ / clients \ / client_list_1.php (8): lib \ App-> define (Object (stdClass)) \ n # 5 {main} "}

thanks I hope for your help I don’t know what to do anymore!