Not all podcasts update on my Macbook in iTunes

I subscribe to a lot of podcasts and I utilize both my iPhone and my Macbook to listen to them. There are several podcasts that update and show new episodes on my phone, but not on my Macbook. When I go into the podcast in iTunes and try to manually refresh that podcast it shows the loading wheel for a second, like it's trying to refresh, but then the updated date at the top (under the podcast's name) still says it updated a date that was several weeks ago. Why are my other podcasts updating when I refresh my entire feed, but not some of them? Why won't some podcasts refresh individually when I attempt to do so? I know there are new episodes for these podcasts because they're showing (and I'm able to listen to them) on my phone.

Any help is appreciated. Thanks!