If the page has a lot of ajax and javascript, you can just wait a bit for the client-side code to finish displaying the page after loading it from the browser.
try it
browser.link(:text =>"Add").when_present.click
If this does not work, make sure the element is not in the frame or something like that.
btw, if the page has more than one link with the text "Add", you may need to specify a container outside the link that allows you to determine which link you want. eg.
browser.div(id: => "divAdd").link.when_present.click
If
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