Maintenance Page is not showing immediately

We have one iRule assigned to the virtual server to display the maintenance page. The maintenance page content is coming from iFile.

HTTP::respond 200 content <iFileContent> noserver "Content-Type" "text/html" "Cache-Control" "no-cache, no-store, must-revalidate, max-age=0" "Edge-Control" "no-store,downstream-ttl=-1" "Pragma" "no-cache" "Connection" "close"

The maintenance page is not getting displayed immediately when we assign the iRule to the virtual server, after few mins it is getting displayed. Not getting what is causing this?

From the logs I can see that the iRule is getting executed but the maintenance page is not getting displayed.

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One thing noticed that, if the URL is already open in browser and then the iRule is assigned then the maintenance page is not coming up immediately.

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But if I close the browser and then assign the iRule.

After that if I access the URL then the maintenance page is coming up.

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Do we need to close the active connection?

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