How many saved searches do you have? You may have reached the maximum.
Try using these alternative links and see if there are any old ones you can delete that may not appear on the other lists:
https://www.ebay.com/myb/SavedSearches
https://my.ebay.com/ws/eBayISAPI.dll?MyEbayBeta&SortOrder=ASCEND&GotoPage=1&CurrentPage=MyeBayFavori...
https://my.ebay.com/ws/eBayISAPI.dll?MyEbayBeta&View=SavedSearches&Column=EmailAddedDate&CurrentPage...
If you have trouble deleting searches, you can also try deleting some saved searches using the app -- that may work more reliably, particularly in cases where the results do not load properly in a browser. Select the search from your saved search list and use the heart icon to unsave, then wait for the cancel option to appear and disappear before going back to the saved search list.
