Failed to swap slots: Cannot modify this site because another operation is in progress.

Question

Failed to swap slots: Cannot modify this site because another operation is in progress.

Finn Kay 0

Failed to swap slots 'staging' and 'production': Cannot modify this site because another operation is in progress. Details: App Service Managed certificate xxx for hostname xxx is being created with http validation for this site. Please wait until the operation is done before proceeding to slot swap.

I get the above message trying to sway staging and production slots since yesterday afternoon. I have worked around by pushing 100% traffic to the staging sot for now but this needs sorting.

I have checked for pending ops and I can't find any, I have tried removing the binding and re-adding along with restarting the service and still I get this error.

Aditya N 1,950 Reputation points Microsoft External Staff Moderator

2026-01-14T09:50:50.2+00:00

Hello @Finn Kay

Thank you for reaching out Microsoft Q&A. We need further information to troubleshoot this issue. I have requested for further information in private message, please provide the inputs.
Aditya N 1,950 Reputation points Microsoft External Staff Moderator

2026-01-14T18:09:43.42+00:00
Hello @Finn Kay

Please could you try the below.

On Azure CLI, you can run:

PowerShell

PowerShell

Invoke-AzResourceAction -ResourceGroupName [resource group name] -ResourceType Microsoft.Web/sites/slots -ResourceName [app name]/[slot name] -Action resetSlotConfig -ApiVersion [version]

Use the Invoke-AzResourceAction command to reset the slot configuration. Replace [resource group name], [app name], and [slot name]

You can also try to restart both the source and target slots can clear any locks or ongoing operations that may not be immediately visible.
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1 answer

Your answer

Aditya N 1,950 Reputation points Microsoft External Staff Moderator

2026-01-14T09:50:50.2+00:00

Hello @Finn Kay

Thank you for reaching out Microsoft Q&A. We need further information to troubleshoot this issue. I have requested for further information in private message, please provide the inputs.
Aditya N 1,950 Reputation points Microsoft External Staff Moderator

2026-01-14T18:09:43.42+00:00

Hello @Finn Kay

Please could you try the below.

On Azure CLI, you can run:

PowerShell

PowerShell

Invoke-AzResourceAction -ResourceGroupName [resource group name] -ResourceType Microsoft.Web/sites/slots -ResourceName [app name]/[slot name] -Action resetSlotConfig -ApiVersion [version]

Use the Invoke-AzResourceAction command to reset the slot configuration. Replace [resource group name], [app name], and [slot name]

You can also try to restart both the source and target slots can clear any locks or ongoing operations that may not be immediately visible.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.

Answer 1

Hello @Finn Kay

I'm glad to hear the slot swap issue has now been resolved.

The error was caused by an App Service Managed Certificate undergoing HTTP validation. During this process, the platform locks the site to prevent configuration changes, including slot swaps. Even if no operations appear in the portal, backend certificate tasks may still be running, which temporarily blocks slot operations.

Once validation completed, the lock cleared automatically—hence the issue resolving after some time.

Reference : https://learn.microsoft.com/en-us/azure/app-service/deploy-staging-slots?tabs=portal#troubleshoot-swap-failures

https://learn.microsoft.com/en-us/azure/app-service/configure-ssl-certificate?tabs=apex%2Crbac%2Cazure-cli#app-service-managed-certificates

Kindly let us know if the above helps or you need further assistance on this issue.

Please "upvote" if the information helped you. This will help us and others in the community as well.

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Failed to swap slots: Cannot modify this site because another operation is in progress.

1 answer

Your answer