If you switched themes and you still have the same problem, that confirms the issue is not being caused by the Mingle theme, and so we cannot help with the issue in this forum.
This forum is only for theme issues, i.e. issues directly related to the Mingle theme.
If you need help with issues that are generic WordPress issues, such as the problem you are currently experiencing, you can ask for help in the dedicated WordPress support forum. → https://wordpress.org/support/
If there is anything about the Mingle theme itself you need help with, please just let us know. If you can’t find a solution using the forum search please create a new topic for each separate issue and we’ll do our best to help.
Thanks.