After you have obtained a license to use the Synthetic Hosted Agent, be sure to check that the license.lic file has the property_eum-hmac-key field that is assigned a keyed-hash message authentication code (HMAC) similar to the following:

property_eum-hmac-key=1a88392cb0004b45b555a854b80f23f5

The HMAC key is used to authenticate your on-prem deployment to the SaaS EUM Server and the SaaS Synthetic Server. Without the HMAC key, your on-premises Synthetic Server will not be able to use Synthetic Hosted Agents.