Unable to connect to Veeam 10 - ERROR: "Cannot find a valid credential." (4246812)

Connection to Veeam failed with:

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ERROR   [Quartz[0]-1086680] com.quest.veeam.agent.VeeamAgentImpl - Cannot find a valid credential.
com.quest.veeam.agent.utils.CredentialNotFoundException: Cannot find a valid credential.
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Trying to connect to Veeam using Rest API failed with:

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{"FirstChanceExceptionMessage":null,"StackTrace":null,"Message":"{\"FirstChanceExceptionMessage\":null,\"StackTrace\":null,\"Message\":\"HTTP Method not allowed\",\"StatusCode\":405,\"Status\":\"MethodNotAllowed\"}","StatusCode":405,"Status":"MethodNotAllowed"}
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