This may be because '%' is not a valid URL character.
Valid URL Characters
There are relatively few valid characters in a URL: uppercase and lowercase letters of the alphabet; digits “0” through “9”; special characters: dash, underscore, period, exclamation point, asterisk, apostrophe and opening and closing parentheses; and reserved characters: percent sign, dollar sign, ampersand, plus sign, comma, forward slash, colon, semi-colon, equal sign, question mark and “@” symbol. All other characters must be encoded using a percent sign and their assigned hexadecimal numbers. Reserved characters, such as the percent sign, are only valid to indicate special meaning, and they must be encoded when they are used without their special meaning. For example, to include a percent sign in a URL, you must encode it as “%25.”
I am going to assume you are using URLs in a table chart:
In my testing, Qlik Sense will convert special characters to their appropriate HTML entity code if the entity code is not used in the data and pass along the URL as-is if it is used in the data.
That is to say, both the links in the example below, produce the same result when a new tab opens.
This is typically not an issue as doing otherwise would produce an invalid URL. As far as I know, there is no domain name with a '%' sign it it such as your example, so there may be a specific context I am missing.