Most of the companies using Joomla CMS for their business websites, from Joomla version 3.0 supported the mobile friendly for frontend and backend. Google also recommend to create the responsive website, this is helpful for to get the better traffic for the websites. Google provided the tool for the mobile-friendly test, this tool helps to analyze the mobile friendly errors. Some Joomla version 3.x websites failed the Google Mobile-friendly test, how can we fix that issues?
Make CSS and JavaScript as crawlable
Most of the Joomla templates create the cache its CSS and JavaScript, if you try to test your website in Google Mobile friendly test, it will get CSS and JavaScript reference from cache folder. But by default, robots.txt file blocked the Cache folder, this the reason your website failed in Google Mobile friendly test. So, you have to enable the cache template folder in robots.txt files. Also, you have made your Joomla template as your CSS and JavaScript as crawlable.
Check Joomla Framework
Nowadays most of the Joomla websites developed with any one of a framework for drag and drop page layout design. But the problem is they are provided the mobile friendly page layout enable or disable options in their template manager. You have to find the option to enable the mobile friendly layout design.
Check iFrame pages
The iframe is the biggest enemy for the mobile friendly websites because most of the iFrame pages fix the height and width. This is the reason your mobile-friendly test will be a failure, you have to check the iFrame pages and make it as responsive. All pages should not fix the width and height, it sizes must be a percentage value.