Add dot ‘.’ after ENE (ENE.) because of that you are getting invalid format.
I have attached a workflow which gives you the Spanish months.
I have two machines. On one machine I have no issues but in another I am getting the same error as you are.
As you can see for every Spanish month it ends with dot.

Uipath_ConvertDate_SpanishToEnglish.xaml (10.9 KB)