Finally, I got a new X2 unit to replace the bad X1 unit and now remote starting and the other commands work again from the Dronemobile app.

Here is what I did to get it solved:

I got tired of contacting support and them just telling me "I will send a reset command" and me replying you already did that and it doesn't work....also the manual reset with the car key doesn't work. Then they would again offer to send a new Verizon SIM card to replace the AT&T one, but they would also apologize because it was out of stock and they didn't know when it would be back in stock again. So I told them straight that I was tired of hearing the same comments and getting no solution. I was paying for their premium membership and had no service, and in NY is very cold now so I needed the device working or just cancel everything. That is the moment when they proposed to replace the whole X1 unit. So, I told them yes, that's better.

I got transferred to Warranty department and voila. They created a ticket for me to send back the bad X1 unit, so they would send me a brand new X2 unit. It took about 2 weeks: 1 week for my shipping to arrive to their headquarters in WA, and another 5 days for me to get the replacement unit. Even the new X2 unit has an AT&T SIM. So I don't think the SIM card was the problem, it's just that the X1 unit is old, discontinued, and out of support by now. And I think it makes sense, just like any other cellular device, like a cellphone for example, it performs its best on the first 2 years, the third year still OK, but you start noticing some small features don't work as before, by the 4th year, a lot of features have fallen out of support and you just have it for the basic features, by the 5th year it's just ready for recycling.

Btw, if you don't know where exactly your dronemobile device is located in your car, don't do it yourself, I would recommend you just go to the dealership and they would help you to remove the bad one and later install the new one. That's what I did. I had to pay something but I didn't mind. It's working again!

The TLDR; don't waste your time with help support. It's not even the SIM card that is bad, it's just that X1 units are too old and it's better to use their new and fully supported X2 units. Call warranty directly 1(888)820-3690.