Hi Rose,
I contacted the hosting company to change the settings to suite System Requirements on XStore Dashboard to Max execution time of 90 , it was 30. Well we have spent all day going backwards and forwards trying to get this 30 to change to 90. They realised there was PHP alt- 7.0 on Cloudlinux and 7.1 on PHP MultiPHP Manager. Now they are both the same the System Requirement for Max execution time of 90. But after all of this when I go into WordPress/Dashboard/Appearance and Customise I cannot see files.