Have you a table defined? And you have some formula in column like ="service"?

When yes, then autofill is switched off whenever something different is inserted into this column - which is logical as Excel doesn't know how to behave after that. And the only advice I can give is to change the formula in this way, that it returns all wanted values, and then copy it to whole column. I.e. don't use entered values and formulas in same column - when you need to enter something manually, add a column and enter manual values there.

Btw. when you manage somehow to make the autofill to work again, then probably your different entry is written ower with formula.