Norton mobile security and mobile balance check

Yesterday, I installed a trial version of Norton Mobile Security.
Meanwhile, the mobile updated the Android to version 5.1.1.

To check my Pay & Go balance I type the code *#100#.
Then the mobile displays the message "USSD code running" but it does not return anything as before...

Do you think that it could be a problem with Norton (maybe blocking the "pop-up window")?


Thanks,

Alex.