Office 365 Attack Simulator is not working

isurudiv 
This might be a little off topic, but I would recommend you to try the new attack simulation training feature instead of the old attack simulator tool found in the Security & Compliance center.

The new feature enables you to use a whole different kind of payloads, and also is able to give the end-user access to trainings.
You can find this new attack simulation training in the M365 Security Center:
1: Go to https://security.microsoft.com/ 
2: Click on the Attack simulation training

Please be aware that this is in preview, but all functions that i've tried have been working just fine.