I had the same error message when importing an .srt file that I had made by hand.
The error message has nothing to do with the header of the file or the format of the .srt.
When only a single subtitle has a duration of 00:00:00,000 Premiere Pro fails to import it.
The solution is to edit the file in a text editor and inspect it whether any of the lines have a duration that looks inconsistent. (overlapping or very short length do not matter). Then correct the file an save it with UTF-8 encoding.
I had the same issue and the YouTube trick is too much complicated.
The main reason why Premiere does not import the SRT file is that it recognises only text files saved with Windows and not with macOS's TextEdit. The latter encodes slightly differently the line breaks.
Here's the method that works all the time: just open the SRT file in BBEDIT (the app is free forever despite the message proposing you to pay to unlock advanced features but you don't need them) and Save As... and be sure to use the following options.
And if the last subtitle does not appear, just add an extra one with dummy content.