Brand New Pool - bleached by pool start up

We have a brand new pool that was put in last summer with a dark liner.
We had the pool company open the pool.
The liner is bleached and looking awful and damaged.


Here's why

The pool has an auto cover
The chlorination was set at 40 as a default
it was supposed be set at 5 because of auto cover.


The pool company says it's our fault because they don't touch the settings
when opening the pool.

WHO'S TO BLAME?

Within the first week or so we had the water tested and were told it was really high, too high for a reading. So we turned it down.

Thanks for your input.