This just happened to me today also. Just reactivated my phone after a repair & am getting invalid card error. It is invalid SIM card error as this phone does not come with a port to install an sd card. What is the fix for this.
I have this same issue. Very unhappy right now, and just upgraded wife's phone yesterday with new contract.
Sent my less than 7 month old G2 in to LG for a warranty repair with a common issue having non responsive screen.
I had to pay to ship it in, and then had no phone for over a week, which people working with and for me rely on me having. I got it back yesterday and turned it on, phone was hard reset and proceeded to reactivate itself, I assume due to being repaired. I of course had to spend an hour putting everything back on my phone and setting accounts back up. Now I get the same error listed stating invalid card, well its a Sprint G2 there is no card. Now I cant get any 4g service which I pay for and expect. I have soft reset, updated prl and profile, no luck. Also noticed that the self service screen pops up which appears also if you select activate device in settings. It states "Because of the type of account you have, we'll need to help you with this task." Wants me to call which I did and could not get resolution. My time is valuable and limited, I pay for something I expect it to work properly. I need swift resolution.......
Thanks for reaching out. I'm sorry to hear of the issues with your G2. If There is a known issue with the Spark capable devices which includes the G2. There is an issue with the devices being able to toggle between LTE and 3G. Some users have reported this error when toggling from LTE and 3G towers. We are currently working on a fix for this issue. In the meantime please try to toggle airplane mode on and off. This will force the phone to find a fresh connection. You may also want to change your devices network mode to CDMA only when in a non LTE area. This should help to stabilize your connection to the network while we work on a resolution.
Sprint Social Care
I have the exact set of issues explained by PANN079. They started after receiving the phone back from LG after a warranty repair. A quick visit to sprint store and after swapping the SIM everything is back to normal. Hope this helps.
Sprint has SIM cards? That's news to me. I have never had a SIM card since 1999, and I don't have one with my LG G2. There is no SD card either. I have had similar issues to everyone on here with my LG G2. I also think it is the phone, not the service. It seems to me that if numerous people are having the same issues with the same phone, there should be some provision for replacing the LG G2 with another phone. How about a recall like they do with cars? I have had my LG G2 since January and I am on my 3rd phone. I got my first replacement within a month of getting the phone. I think it is ridiculous and unfair that a new phone is replaced with a refurb if it is under warranty.
I had to check to see if I had posted this. I am having exactly the same issue, started around the same time, and I had also sent my phone to LG for the same display issue. I have called Sprint Support about a dozen times and went to a Sprint store twice. Still no resolution.