There’s another option, that doesn’t require you to have screwed up the FTP test or to do the VO2max intervals at 100%. The relationship between your FTP and VO2max could be different, probably due to lack of VO2max training. When the workout calls for 120% of FTP, if you do 117% (or thereabouts), does that make the whole workout more doable? If so, then doing all the intervals at slightly reduced intensity should be better than skipping later intervals because the earlier intervals were too hard.
The most important thing about VO2max work is accumulating time at a high percentage of VO2max, not the exact power numbers. The power numbers are a guide for what effort is required to start accumulating time, but more time is more valuable than less time, as long as you are operating at a high percentage of your max.