Not able to turn on the Audit Log Search

Typically you would need permissions to be assigned on the Purview Portal in order to accomplish this. Please refer to the documentation here- https://learn.microsoft.com/en-us/purview/audit-search?tabs=microsoft-purview-portal#before-you-search-the-audit-log

There is a pre-requisite to have the Audit Manager role or the Audit Reader role groups on the Permissions Page. Under Settings, find Role Groups and then Audit Manager role group which you should assign yourself. Once done, proceed to test your scenario. As best practice, wat for changes to propagate