One problem related to transmission not engage has been reported for the 2015 Honda Odyssey. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2015 Honda Odyssey based on all problems reported for the 2015 Odyssey.
Transmission power has started to fail to engage fully at highway speeds or low speed sudden acceleration. The third party shop showed me a Honda service bulletin 17-043 stating the transmission fluid deteriorates faster than normal. Somehow a software fix is going to address this problem.