Hi, SUE
Thanks for reaching out.
My name is God'swill, I'll be happy to help you today.
For some reason the default in Teams for "Calculation Options" under the "Formula" tab might be set to manual/automatic.
Try changing is to automatic if it's on manual or the other way round, once it is changed it will work as indented.
Please be sure to let me know if you need more help as I'll be glad to do so.
Regards...
God'sWill