I can send a text message, but I can no longer see the replies.

Is the reply in the inbox on the Explore web site? This is the first thing to check. If it's there, it SHOULD eventually make it to the device. If not, the problem is between your wife's phone and the Garmin servers.

In case you don't know: The ability to reply to a given text message from an iR device is time-limited. It's on the order of a few weeks, not minutes or hours. The time limit is not exact, but the ability to reply definitely does expire. This has to do with the fact that the Garmin servers need to remember some things about the original SMS from iR to phone in order to route the reply properly. To keep things cleaned up, the servers "forget" that information after a while.

So, if your wife is replying to an old message, it might not make it back to your device. If the reply is NOT in your inbox on the Explore site, this is the likely explanation. If it's a reply to a recent message, this doesn't apply.

Another possibility is that there is a specific problem with your wife's cell phone provider. I've never seen an example of this with a reply. But it has happened several times with messages from iR to phone, specifically with AT&T. They have aggressive anti-spam filters which in some cases dropped messages generated by the Garmin servers because they contained certain forms of shortened URLs. I haven't heard of this lately, though.

I assume that you did a "mail check" from the device, rather than just waiting for the reply to arrive? The device will do an active check whenever you send something (another message, a track point, or whatever). And I think that even the legacy devices like the Explorer+ automatically check once an hour. My only point is that if you just wait, you might wait for up to an hour. There are some special provisions to enhance "conversation", but those only apply if the reply arrives within a few minutes of the outbound message. And I'm not entirely sure that the legacy devices have that feature.

Also, you mention the Earthmate app. Did you also check the device itself? Just trying to eliminate as many variables as possible.

If it was a reply to a recent message and it's not in the inbox, I'd call tech support.

If it's in the inbox but not on the device, do a mail check on the device itself (without messing with the app). If that does not deliver the message, I'd call tech support. 

Thanks for getting back to me. The last time anyone was able to text me back was back in Oct, 2019. Each time I go out hiking I will send the normal tracking message that I've started my hike. Then along the hike i will say did you guys get my message and I won't get a reply back, but they are getting my messages and are sending replies I just don't see them. Also I did look at the Inbos on Explore and you can only see my messages sent no replies. I've attached an example of what i see. 

Call tech support.