Thanks for alerting us. Looks to be a tech gremlin at work... we'll get it fixed as soon as possible.
Meanwhile, one option is to use the SEARCH page at www.soundonsound.com/search
and enter the following text string into the search box:Published+April+2019
(no spaces, must use + symbols)
This will then display a list of all articles and news, so narrow your search by clicking on the ARTICLES tab on the Search page. This link will get you there instantly
For different months, simply amend the Month name, eg:Published+March+2019