Dynamic mode does not change in the infotainment sytem
 

Yes. I've also experienced this on my '17 Civic Si and '18 Accord.

The RDX's Owner's Manual says:
"Dynamic Mode Change Unavailable
Appears if the dynamic mode cannot be changed due to certain situations, such as a system error or adverse driving conditions."

Generally, you'll see this message appear under certain driving conditions where a sudden change in the vehicle's dynamics (steering, braking, acceleration, suspension) could upset the chassis leading to a loss of control.

any updates on this? I just had this pop up today... couldn't change the dynamic mode.. and also the Nav screen changing from day to night, and back, every 30 seconds for a brief moment. Full daylight out. Sometimes with a message saying dynamic mode change not available.

weather cold, clear, but not unusual... maybe 18 degrees f?

drive mode change not available
 

Just had drive mode change not available pop up several times also experienced the Nav screen bouncing back and forth between day and night several times. Less than 500 miles. Temperature about 36 at sunset.

Yes, a few of us have seen the same thing. This only happened to me once in late December 2018 after the software update to 1.0.7. It happened while driving and does not appear to relate to temperature and time of the day.
For me,. stopping the car, get out, lock the car, and came back to start it after about 20 minutes fixes it.

It's pretty sad when people have to reboot their cars to get them to work again. I feel like we've regressed to Windows 3.1.

Check your config.sys and autoexec.bat...

Drive mode actually still changes, but no picture
 

This happened to me about a month ago. It was just a normal clear day and there were no other warning lights--go figure. What was interesting that the drive mode actually DOES change, but you don't get the fancy picture in the infotainment display. You'll see the new drive mode reflected at the bottom of the instrument panel. The next time I started the engine, the problem went away. There are some other threads here on this.

And software is probably not even the weakest link in the chain. With everything being drive by wire, your only physical connection to the car is the steering and the brakes, and even with those, just barely. There are so many motors, controls, servos, synchros, solenoids, linear actuators, rotary actuators, sensors, feedback loading, etc. I know the components have gotten much more reliable over the past 20-30 years or so but it's still surprising, something doesn't break every day. Especially considering the environmental extremes everything is subject to.

This happened to me a couple times. Pressing the D/S button while already in Drive resolved it. Something in the manual about it but I forget what the logic is.

That would switch the transmission controller into "Sport" mode ( Or S mode if you prefer... ). Dunno why that would get the "Dynamic mode" stuff out of its snit.

But if you want your mild-mannered RDX to get some serious attitude, set the dynamic mode to Sport+ and the transmission to Sport. Yee Haw!

The terminology used in the manual for the transmission is Drive / Sequential. I'm not sure what they mean by sequential or how D/S relates to the dynamic modes. I still mean to get out on some deserted roads and wring it out to undrstand what all the differences are.

What (I think) I've experienced so far:
Snow: I haven't used it or needed it yet.
Comfort: Normal automatic transmission operation. Using a paddle shifter will upshift or downshift and display the actual gear on the dash. But it will resume normal automatic operation within a few seconds.
Sport: More aggressive shift map. Once you use a paddle, you need to shift manually thereafter. Maybe it returns to auto at some point, I don't recall.
Sport +: You must use the paddles and shift manually.

Not sure exactly how D/S affects the modes and I need to experiment more.

Did you get the new software patch? Had the same issues one time but not since the February patch. Super quick install at the dealer. Service writer says their computer and the car were "talking" about the patch the minute we drove in.