A family of Microsoft relational database management systems designed for ease of use.
Based on the question (item 1)
"1) Setting it over the options for the current database"
they have done exactly that already and have the issue they are asking assistance with
Based on the statement
"the title bar still shows the Access icon but in the task bar the correct custom icon is displayed."
It is clear they have properly set the property, but the issue lies with Windows/Access.
I gotta said your answer sounds a lot like generalized AI content.