Google launched a mobile testing tool a few months back and since then, Google has been educating webmasters around how the tool works and what prevents it from working.
Such as blocking or cloaking GoogleBot can set it off on the wrong path.
But did you know, the tool is also slow to update when you change your robots.txt file?
One webmaster complained in the Google Webmaster Help forums that the tool was not working because of an error.
Eric Kuan responded in the thread saying that the Mobile Friendly Test tool can be delayed in discovering the update to a robots.txt file. So if you were blocking it and then opened it up, it still can take some time to work.
Eric wrote:
The mobile-friendly test should be working for you now. When you make changes to your robots.txt file, it can take a little time for the Mobile Friendly Test tool to recognize that the robots.txt file changed.
Forum discussion at Google Webmaster Help.
