Transmission not shifting after service

I have a 2004 Dodge 1500. I just changed out the filters and transmission fluid about a month-and-a-half ago, a short time later it started having trouble shifting. Now it will periodically go into second gear while in drive but won't shift any further. I understand that it could be a sensor but I'm wondering if there is something I did or did not do while servicing the transmission that could cause it to do this and what could potentially be a fix. Assuming at the moment that I'm going to have to switch it out. Any advice would be greatly appreciated thank you and have a great day. JM