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Overide the file

vendor/magento/module-ui/view/frontend/web/js/view/messages.js

TO

app/design/frontend/YourPackage/YourTheme/Magento_Ui/web/js/view/messages.js

Comment Out the below code,

onHiddenChange: function (isHidden) {
var self = this;
    // Hide message block if needed
    if (isHidden) {
       setTimeout(function () {
              $(self.selector).hide('blind', {}, 500);
       }, 5000);
}

Finally execute upgrade,Content commands