# Synthetic monitor creation failed with 401

**URL:** <https://community.dynatrace.com/t/synthetic-monitor-creation-failed-with-401/40544>\
**Category:** Synthetic Monitoring\
**Tags:** browser-monitors, synthetic-monitoring, private-synthetic-locations\
**Created:** [July 6, 2023, 8:30am UTC](https://community.dynatrace.com/t/synthetic-monitor-creation-failed-with-401/40544 "2023-07-06T08:30:10Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Islam\_Zedan](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/islam_zedan/32/31999_2.png) [@Islam\_Zedan](https://community.dynatrace.com/u/Islam_Zedan)\
**Post date:** [July 6, 2023, 8:30am UTC](https://community.dynatrace.com/t/synthetic-monitor-creation-failed-with-401/40544/1 "2023-07-06T08:30:10Z")

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Hello,

We are facing an error while we try to create a synthetic monitor on the customer environment, checking the log we found the below error

[browser-BeaconSenderService-thread-1910] WARN BeaconSenderService: Failed to send beacon BeaconData[beaconEndpoint: [https://localhost:9999/beacon/synthetic/browser/xxxxx-xxxx-xxxx-xxx-xxxxxxx?flavor=cors&app=xxxxxxxxxxxxxxxxxxx](https://localhost:9999/beacon/synthetic/browser/xxxxx-xxxx-xxxx-xxx-xxxxxxx?flavor=cors&app=xxxxxxxxxxxxxxxxxxx)&nbsp;type: MessageType{value=‘BeaconRequest’}, beaconId: 1], got 401 (token: \*\*\*\*\*####))

Any ideas why the AG can’t authenticate with the cluster server.

thanks,

Islam

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**Author:** ![hannahmac](https://avatars.discourse-cdn.com/v4/letter/h/dec6dc/32.png) [@hannahmac](https://community.dynatrace.com/u/hannahmac)\
**Post date:** [July 6, 2023, 8:37am UTC](https://community.dynatrace.com/t/synthetic-monitor-creation-failed-with-401/40544/2 "2023-07-06T08:37:21Z")

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Please can you create a chat or support ticket so we can check the Synthetic tokens are not stale in you environment.

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**Author:** ![radek\_jasinski](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/radek_jasinski/32/10432_2.png) [@radek\_jasinski](https://community.dynatrace.com/u/radek_jasinski)\
**Post date:** [July 6, 2023, 9:34am UTC](https://community.dynatrace.com/t/synthetic-monitor-creation-failed-with-401/40544/3 "2023-07-06T09:34:06Z")

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Hi&nbsp;[@Islam\_Zedan](https://community.dynatrace.com/user/16821)

Please note that you are trying to send a beacon to localhost. Have you verified the configuration of your AG and synthetic monitor?

Radek

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<div class="post-metadata">

**Author:** ![hannahmac](https://avatars.discourse-cdn.com/v4/letter/h/dec6dc/32.png) [@hannahmac](https://community.dynatrace.com/u/hannahmac)\
**Post date:** [July 6, 2023, 9:59am UTC](https://community.dynatrace.com/t/synthetic-monitor-creation-failed-with-401/40544/4 "2023-07-06T09:59:52Z")

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This is expected in a Private ActiveGate. The beacon goes to the localhost and is redirected to the cluster. The logs just show the localhost connection

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<div class="post-metadata">

**Author:** ![radek\_jasinski](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/radek_jasinski/32/10432_2.png) [@radek\_jasinski](https://community.dynatrace.com/u/radek_jasinski)\
**Post date:** [July 6, 2023, 10:03am UTC](https://community.dynatrace.com/t/synthetic-monitor-creation-failed-with-401/40544/5 "2023-07-06T10:03:02Z")

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Yes, you are right!

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<div class="post-metadata">

**Author:** ![Islam\_Zedan](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/islam_zedan/32/31999_2.png) [@Islam\_Zedan](https://community.dynatrace.com/u/Islam_Zedan)\
**Post date:** [August 6, 2023, 12:06pm UTC](https://community.dynatrace.com/t/synthetic-monitor-creation-failed-with-401/40544/6 "2023-08-06T12:06:02Z")

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The problem solved after opening a support ticket, to fix the token issue.