Tag clouds problem

Have you tried using the default widget to see if that works? Might need to reset your permalinks as well perhaps something is just getting hung up and needs to be reset(resaved). Hope this helps.

https://wordpress.org/support/topic/tag-cloud-not-working-1?replies=5

In case you’re not sure how to reset permalinks this is a good quick guide.

https://modernthemes.net/documentation/resetting-wordpress-permalinks/