hasStrings and strings properties of UIPasteboard.generalPasteboard have a problem

In iOS14, I checked,

Code Block 
if (UIPasteboard.generalPasteboard.hasStrings == YES) {
	NSArray *stringsFromPasteboard = UIPasteboard.generalPasteboard.strings;
}

but stringsFromPasteboard is an empty array though if-statement is YES.
For example, all is fine immediately after I copy some string from Safari. In 20 minuetes, I retried to above code but, the issue is triggered.
Then, if I just touch the text field, paste button is popped up. And if I touch the paste, nothing pasted.

I want to check whether or not UIPasteboard has strings. If has, wanna get the strings.