Problems with measures including dynamic format

Hii dev_almeida 

Dynamic format strings only persist for measures created in models that support it (DirectQuery/composite models or models edited via Tabular Editor). In older Desktop builds, the dynamic format can silently reset after confirmation. Make sure you’re on a recent Power BI Desktop release, enable Dynamic format strings in Preview features, and define the format using the Format string expression (not the standard formatting pane). If it still disappears, create or edit the measure in Tabular Editor that’s the most reliable workaround until the behavior is fully stabilized.

i dev_almeida you Dynamic format strings should be placed under dataset (tables). You could find it by a calculator icon. 

And use correct method to create it: Measure Tools → Format dropdown, select "Dynamic"

It will be look like this: 

Thanks