Returning is harder than starting, and almost nobody warns people about that, so I will.
Why it is harder
A beginner has no reference point. Whatever happens in the room is simply what yoga is, and there is nothing to compare it against.
Someone returning has a very detailed reference point, and it is of themselves at their best. Every position is being silently scored against a version of you that practised four times a week in 2019, and that scoring is relentless and unhelpful and happens automatically.
What actually comes back, and how fast
Faster than you fear, in this order: coordination first, then endurance, then range, then strength. The pattern recognition is largely intact, which is why the first class feels strangely familiar and the second one feels awful.
The second class is the honest one. Go to a third.
The mistake
Starting at the level you left off at. It is the single most common way a return ends in a strained something within a fortnight, and the reason is that your nervous system remembers the position while your tissue has not been loaded in years.
You can do the shape. You cannot yet afford it.
What to do instead
Go one level below where your pride puts you, for three weeks. Not one class, three weeks. Then reassess.
Tell me on the way in. Not the full history, just that you are coming back after a long break. It changes what I offer you and it takes five seconds.
The gap was not wasted
Whatever happened in those years happened, and a lot of it was more important than a yoga class. People come back after illness, after a bereavement, after a decade of small children, after work swallowed everything.
The practice did not go anywhere and I do not need an explanation. This is a room with a timetable, and you can walk into it on a Tuesday.