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The 'Discover page' must be enabled for the 'Topic Search' beta feature to function correctly.
In order to resolve this issue, you can:
Disable the 'Topic Search' beta
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feature
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or
Keep the 'Topic Search' beta feature enabled and enable the 'Discover page'
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If you keep 'Topic Search' enabled and then enable the 'Discover page', the search experience will be updated to the new 'Topic Search'
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.
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