Where has the symbol gone in Excel that used to convert text to numbers?

Your screenshot still shows green triangles beside the H/Count values, so Excel is flagging those cells; the conversion feature has not necessarily disappeared. Select one flagged data cell, rather than the table heading, and press Alt+Shift+F10 to open its error-checking menu. Choose Convert to Number if that is the reported issue. Once that works, select the remaining affected cells and apply the same action. If the menu remains unavailable, use an empty adjacent column with =VALUE(A2), replacing A2 with the first count cell, then fill down. Check the converted results before copying them back with Paste Special, Values. This gives you a supported conversion route without depending on the warning button. Avoid changing the entire worksheet indiscriminately. If the keyboard shortcut also fails, provide your Excel version and whether the same test works in a new workbook; the screenshot alone does not establish a removed feature.