New training 10km program unable to be created.

Same here. Did you manage eventually ?

I also have this problem! Anyone got a solution?

What date did you try to set for your race date? In the handful of instances this issue has occurred to me, it's because I set a date farther than the plan can create. This is especially possible when you try to do it on the website, where it's easier to input an unsupported date. This can also occur on the mobile app, even when it shows the date is available.

I'm not completely sure what causes the issue, but my workaround is to create a plan set the date a day or two after the upper limit of the suggested plan. For example, if I have a race date of November 7 for a 16-week Greg McMillan plan, I'll create the plan a day or two after July 18.

Yes, it's annoying that I'm not able to create a plan with more time than I need, but I'll enjoy the extra few days before I have to start. ;)

I didn't change the suggested date.

But when i tried to start a new coach program the day after it suddenly worked! Maybe there's a bug that keeps me from starting a new program the same day I completed the previous?

Yeah, I wouldn't be surprised if Garmin Coach thought that you were trying to do two training programs at the same time, which isn't possible as far as I can recall.