Sagging liner

[rflorestal]

Just wondering if anyone can advise me on this sagging liner before calling for technician. I have actually used hot water and have managed to put back a big portion of the liner. However, this corner piece as you can see from the picture has proven to be difficult.
Please advised. I live in the northeast and have to close soon. Thanks for your help on this.

 

[wireform]

If the liner is old it may not go all the way back as it has its limitations from age as to how much it'll stretch but trying your best won't hurt. I see it needing two people working it from both sides with hot water and rags massaging the liner as you move along.