Hello,
I would recommend you to check Search Tier. You are likely to encounter this issue if you are exceeding the limit, like you just create more KBs than the limitation.
The maximum number of knowledge bases is based on Azure Cognitive Search tier limits.
For example, if your tier has 15 allowed indexes, you can publish 14 knowledge bases (1 index per published knowledge base). The fifteenth index, testkb, is used for all the knowledge bases for authoring and testing.
If this is your case, you could consider for an Upgrade the Azure Cognitive Search service https://learn.microsoft.com/en-us/azure/cognitive-services/qnamaker/how-to/set-up-qnamaker-service-azure?tabs=v1#upgrade-the-azure-cognitive-search-service
Hope this helps.
Regards,
Yutong