Dashboards use $ to denote fields requiring input, such as $earliest, $latest, etc. It's probably failing to correctly parse that.
Try escaping the dollar signs in your search by doubling them up:
match(RelativeURI,"/identity/enhanced-authentication/tasks/~/search") AND match (HttpMethod,"POST"), "TASK1",
match(RelativeURI,"/identity/enhanced-authentication/tasks$$") AND match (HttpMethod,"POST"), "TASK2",
match(RelativeURI,"/identity/enhanced-authentication/tasks/*") AND match (HttpMethod,"POST"), "TASK3",
match(RelativeURI,"/identity/enhanced-authentication/tasks$$") AND match (HttpMethod,"GET"), "TASK4",
match(RelativeURI,"/identity/enhanced-authentication/tasks/*") AND match (HttpMethod,"GET"), "TASK5")
... View more