What is the problem in Leroy and Norma Jean's marriage in "Shiloh"?

Norma Jean and Leroy have grown apart during their marriage, and now an inability to communicate clearly plagues them. Because of Larry's accident, he is now at home all the time, a fact that bothers his wife. She became accustomed to his long absences as a trucker, and she had begun to develop some independence. Her efforts to improve herself continue as she looks to the future. Leroy, on the other hand, is trapped in the past. He wants to build her a log cabin (she isn't interested in the least), and he's confused by the changes he sees in Norma Jean. Their gender roles seem to have reversed: he now makes needlepoint pillows but she lifts weights and supports the couple. The only reason these two married was an unexpected pregnancy that resulted in the birth of their only child Randy, a baby who died of sudden death syndrome fifteen years ago. The couple now has little in common. He yearns for the past while she seeks change and the future.

Why is the marriage of Leroy and Norma Jean in "Shiloh" by Bobbie Ann Mason suffering?

"Shiloh" is a short story by Bobbie Ann Mason, appearing in both The New Yorker magazine in 1980 and in her 1982 collection Shiloh and Other stories.

Leroy has injured his leg and cannot drive his truck for work. Norma Jean, used to his absence, finds that she does not want to live with him home all the time, and more so with her mother showing up to criticize and comment on every little thing. Worse, neither of them seems to care or even notice that she is suffering. Norma Jean wants Leroy to seek work and be productive, and also wants him to appreciate all the work she is doing to keep them financially secure; she is working hard and trying to improve herself:

Something is happening. Norma Jean is going to night school... "First you have a topic sentence," she explains to Leroy. "Then you divide it up. Your secondary topic has to be connected to your primary topic."

Even Leroy's epiphany at the end is couched in his own terms, and he loses focus:

Leroy knows he is leaving out a lot. He is leaving out the insides of history. History was always just names and dates to him. It occurs to him that building a house out of logs is similarly empty -- too simple. And the real inner workings of a marriage, like most of history, have escaped him. Now he sees that building a log house was the dumbest idea he could have had.
(Quotes: Mason, "Shiloh," Google Books)

Leroy cannot understand what Norma Jean is missing in her life; he only sees his own problems and what he thinks are her desires (a house). His inability to connect with her emotionally is the underlying problem in their marriage, as is her need to keep her feelings suppressed until they burst out at the end, instead of sitting down and talking things through.