Hi @IniobongNkanga-8038 ,
As per your description, may I know have you tried to Reindexed the list and tried search for list item after 2-3 minutes? via go to List Settings>Advanced settings>Reindex List under the "Reindex" section.
Note: sometimes it takes time to re-index lists.
Also, try disable search on site. click ok. After few minutes enable search on site. Sometimes it will work in my experience.
You could refer to following document
https://learn.microsoft.com/en-us/sharepoint/crawl-site-content
And if reindex doesn't fix the issue, you could refer to the steps in the similar issue
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