Hi Seana,
Please do following steps:
> Portal
1.1 There are 2 requests on knowledge article details page source code:

The above one is for updating views record, the below is for retrieving the toal count.
You could check whether those two requests exist on page source code,
1.2 Refresh article detail page and open F12 developer tools to check whether updating request has been sent successfully(200 code stands for success).

1.3 Copy Web API link below and execute it directly in browser,
https://org.crm.dynamics.com/api/data/v9.0/knowledgearticleviews?$filter=_knowledgearticleid_value eq 'knowledge article id'(You can find this id in last position of address bar URL link when you're browsing a specific knowledge article data in CRM in UCI)
A view record shall be generated(when you first enter the article detail page) or the knowledgearticleview value will be updated(when you first enter the page then refresh page)

1.4 If you got no result from above steps, you could remove Access Control Rules on Knowledge Base - Article Details

1.5 If there are not any rules in the tab, you could try reset Portal.
> CRM
If you could get success from above steps, you could check whether any customization made on the record views subgrid, such as you may have changed view for that subgrid.
> Support
Because source code of Knowledge article detail page is not accessible in Portal for us,
so if all of above steps not work,
please open a support ticket.
Best Regards,
Leo