Problem with Tags on blog articles

Hi!

I am experiencing a very strange issue regarding the tags on my WordPress-built website (https://innovationschool.talentgarden.org). A lot of the articles in the blog have tags assigned to them, but when I type the page associated to that specific tag on the browser (e.g. https://innovationschool.talentgarden.org/tag/business-data-analysis/), it returns an empty page that simply has the word “index” on it, instead of showing the articles that have been tagged as “business data analysis”.

Also, none of the tags has been indexed by Google. I’ve checked the robots.txt on the site and it seems fine.

Why is that happening? How can I fix this issue?

Please help me! It would be very much appreciated.

Many thanks!
Sara