I am also facing this issue. I set service level to “platinum” for a service, create a notification rule to match service level platinum. Then I test notification and I get 0 matches.
Version: Checkmk Raw Edition 2.4.0p18
Test results
0 notification rules are matching (0 global rules, 0 user rules)
0 notifications would have been sent based on your notification rules (see table: ‘Predicted notifications’)
See the following tables for more details.
Notification rule condition:
My service has platinum level:

Example test:
EDIT:
I checked var/log/notify.log in my OMD site and can see this:
2025-12-29 15:22:55,668 [20] [cmk.base.notify] Analysing notification (<REDACTED>) context with 85 variables
2025-12-29 15:22:55,668 [15] [cmk.base.notify] Global rule 'Notify critical event for business critical services with Platinum Level'...
2025-12-29 15:22:55,668 [15] [cmk.base.notify] -> does not match: The service level 0 is not between 30 and 30.
2025-12-29 15:22:55,668 [15] [cmk.base.notify] Global rule 'Notify host critical event for business critical services'...
2025-12-29 15:22:55,668 [15] [cmk.base.notify] -> does not match: This is a service notification, but the rule just matches host events
2025-12-29 15:22:55,668 [15] [cmk.base.notify] Global rule 'Notify all contacts of a host/service via HTML email'...
2025-12-29 15:22:55,669 [15] [cmk.base.notify] -> does not match: This rule is disabled
This is the clue I’m looking for. Looks like service level is not applied?
does not match: The service level 0 is not between 30 and 30.
EDIT 2:
Test host I am testing with is a clustered service. There may be an issue with how custom service attributes are handled. Livequery to confirm:
$ lq "GET services\nColumns:custom_variable_names custom_variable_values\nFilter: service_description = Service <redacted>"
EC_SL;30
I have another host which is not a clusterd service and here the service level works as expected when I do testing
So I am not sure at this point, is it only in test mode service level fails or also in real events? And does it only fail for clustered hosts?