Passly was originally released as AuthAnvil. AuthAnvil was also originally an On-Premises deployed solution that integrated with many third parties. We still maintain this URL for those older integrations.
If you would like to use some of the older integrations that were you designed for use with the On-Premises version of AuthAnvil you will need the SAS URL.
For the older AuthAnvil On-Premises it looked like this https://(Your Domain)/AuthAnvil/SAS.asmx
For an AuthAnvil On-Demand tenant it will look like https://(Company Name).my.passly.com/AuthAnvil/SAS.asmx
Note: the (Company Name) will be dependent on the name you chose for your Passly tenant.