Can you dial 500 (Voicemail) or 600 (Echotest)?
Also try *500 and *600 to check if your ATA is allowing leading[*] when dialing out.
Try *266300 (Test call via SipBroker).
Try *18005558355 (Tell Me service)
These calls are automatically handled by the Voxalot default dial plan.
Try to reach your Voxalot extension using one of the SipBroker Access numbers.
SIPBroker - PSTN Numbers
After reaching the Sipbroker service, dial *010xxxxxx and # or [Send] (xxxxxx=Voxalot Account Number).
This format works independently of which server you are logged on to.
I usually set my ATA expiration time to a lower number than 3600 (120 to 600 seconds).
For other call testing using Registered or unregistered PSTN type providers, you will very likely need a Dial Plan set-up.
Configuring Smart Call (Dial Plan) Settings - Voxalot FAQ
You can also try logging onto a different Voxalot server (Eg us.voxalot.com).
If you do that, identify the preferred cluster on your log-in page to match, although I am not sure if it really makes a difference.
Rgrds