I have multiple tables in different tabs in my spreadsheets that I reference. Most of the time, when I start writing a formula against a table in a different tab, as I type the table name, a list of possible names shows, and when I type an opening bracket, the list of headers for that table appears. For about 3-months, some of my older tables allow me to see the table name as I type, but the corresponding list of headers does not appear.