Wow, you’re me, on a delay. It’s taken me three weeks to come back from the flu (counting from when I felt well enough to get back on the bike), so now I can speak with Authority™ 
: Take it easy and be patient. Sick weeks are not rest/recovery weeks, they’re high-stress damage weeks that suck the fitness right out of your bones, but it’ll come back. Take an actual rest week when you’re actually feeling better, back up a couple weeks in the plan, and expect to work at a lower threshold while your body puts itself back together. (If you used the Plan Builder, TR has some alternative modifications.)
Maybe a really intense one? But it’s ok to carry some fatigue into the test, and it might even be better for your future training.