I'm working around with TYPO3 7.6.7 and realurl 2.0.14 . Currently I'm stuck up with the following trouble. I configured realurl manually and after enabling realurl I'm getting 404 Not found error. I've read number of questions here itself, regarding the same issue. But unfortunately I'm still in the maze. Few of the solutions were restarting apache, cross checking 'rewrite mode on' in .htaccess and clearing cache(I seriously don't think so). The point is there isn't any answer explaining what the real problem is. To my wonder, realurl generated url is as it is supposed to be. Really desperate enough to try any possible solution.
In quite some cases this was caused by a cHash mismatch. Usually the Install Tool setting $GLOBALS['TYPO3_CONF_VARS']['FE']['pageNotFoundOnCHashError'] is set to 1 which triggers the 404.
The 404 is intended behaviour, because a cHash mismatch usually indicates that URL parameters are manipulated.
I haven't tracked down the cause of the error in all cases. In a few cases pw_comments added parameters to the URL; in these cases it was enough to add the parameters to the list of parameters which need to be excluded for cHash calculations. In other cases it might be a bug in RealURL (since everything works without RealURL active).