Your sash windows have been freshly decorated and there is no longer room in the frame to travel lower down if you ve pulled the window forcefully it s now stuck firm.
Sash window weights stuck.
Feed a new length of sash cord over the pulley on each side jamb and down into the wall cavity.
Prying off the window trim may or may not give you access to the weights but you won t know.
Pull one of the sash cords until the sash weight hits the pulley then lower the weight about 3 inches.
For a window without access panels you also need to remove the window casing.
Windows old enough to have sash weights have probably seen a variety of painters of various skill.
Pry the old sash cords from the sides of the window sash.
How to replace window sash weights accessing the weights.
Access the window sash cords.
Remove the window and then open the panel cover on the side jambs to access the sash cord weight and pulley.
Set the sash partially into the window opening.