The following versions of the Azure Cognitive Search REST API were retired by Microsoft and are no longer supported starting from 15 January 2021:
This affects Sitecore XP 9.0 Initial Release and Sitecore 9.0 Update-1 solutions on Azure using PAAS installations and Azure Search.
For more information about API versions in Azure Cognitive Search, refer to the following link:
https://docs.microsoft.com/en-us/azure/search/search-api-versions
To resolve the issue, consider one of the following options:
Be aware that the hotfixes were built for the specific Sitecore XP versions and must not be installed on other Sitecore XP versions or in combination with other hotfixes. In case any other hotfixes have already been installed on a certain Sitecore XP instance, send a request for a compatibility check to Sitecore Support.
Note that the ZIP file contents must be extracted to locate installation instructions and related files inside. The hotfix must be installed on a CM instance and then synced with other instances using standard development practices.