LO 6.0.4-Calc - why changed the font type?

While making a calc worksheet, I selected the font type, the currency type, and when finished I saved it.
However when I open this worksheet to make more entries (or updates), the font type is not what I selected, had to select it again, same with the currency.
Have I done something wrong ?
Answers will be appreciated.
OS is win 10 pro 64 bit, English version

Did you save as ods or xls(x)? If it is Excel format it could be a conversion mistake.

If it is saved as native ods format so upload a specimen for more research…

… or was that CSV by chance (which cannot hold any kind of formatting in principle)?

To the first comment above: I saved the worksheet (calc) as (Excell) Filename.xlsx, when I open it to add/update entries, have to select again my favourite font type, same for currency.