How to translate text added in the customizer sections

Hi,
I am trying to translate the strings added into the customizer theme options.

I have tried to add the strings in the string translations by adding these function in functions.php

pll_register_string( 'string', 'I nostri prodotti', 'polylang', true );

but when I filled in the input in the string translation table, nothing happens.
When I switch to the eng language the string is still in Italian.

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