For two months now the Sort function is not working. When I choose SORT by sender it only reverses the emails from the oldest to the newest. I have contacted Comcast on at least 4 different times about the issue and they have provided me with Ticket #s when they escalate it to a higher technical support. Never has it been fixed. Then they call me to fix it from my end or to explain to me how to sort. If I know it's no longer sorting by sender then obviously I know how to do it. I have tried it with Chrome, Firefox, Edge, IE and from two different locations. Obviously, it needs to be fixed by Comcast, not me. I am extremely frustrated while my emails continue to pile up. It's the only way I can delete/clean up my email box.
I had the same problem recently and went through the same frustration that you are going through. I checked the Forums and found many suggestions including switching browsers, etc. I came across a very easy suggestion and tried it. It worked for me and hopefully it will for you. I too use the sort "From" to clean out my In Box & Trash. When you press "Sort By" and get the list of sorts, look at the last choice - it should be "Conversations" - If that is checked (mine was) uncheck it and try the "From" sort again. As I said, it worked for me and have not had the problem again.