I am having problems when I am using grouped worksheets

eg. In the one where I enter data/formula, I enter +c6*.5
This then correctly adjust the formula with the correct result and using say
a value of 30 in cell c6, it correctly produces the result 15

However in all the other sheets, it shows +R[-3]C (i.e. relative references)

I believe my settings may have changed - I have compared all the settings in
Excel with another user & he does not have this problem

Is this therefore a problem with the default template or something else?
Hope you can help