Hi @ebm1001 ,
Do you mean that you could not use ID field in search function?
Two reasons:
1)search function only works for text type field, ID field is number type
2)Textinput.Text represents text , not number
To solve this problem, you need to add a text type column with the value of ID and search based on this field.
Try this function:
Search(
AddColumns(my_SP_List,"id2",Text(ID)),
TextSearchBox1.Text,
"a", "b", "id2")
What's more, the delegation problem that @Drrickryp said may affect your issue too, but not the key problem.
Could you tell me how many records are in your sharepoint list?
If it is less then 2000, you just need to change the delegation limit to 2000 to avoid the effect.

If it is larger then 2000, I suggest you save data to collection then filter based on this collection.
I do not suggest you use startswith function to avoid the delegation limit because startswith function and search function are different feather. Number type(ID field) is not delegate for startswith function neither.
Just need to do this:
set the app's OnStart:
ClearCollect(collection1,my_SP_List)
set the gallery's Items:
Search(
AddColumns(collection1,"id2",Text(ID)),
TextSearchBox1.Text,
"a", "b", "id2")
Best regards,