Had you ever taken the slide off? Thread protector? Will the.mag come out? Did you ever fill mag? Is there a case stuck in chamber?
If the mag comes out and no round in chamber you can pit a cleaning rod through barrel and and tap it loose.
If there is an in fired round it chamber I would try different approach.
If you took thread protector off to test fit the thread adaptor you may have left the recoil spring retaining washer off. That would cause recoil spring or a small part of it to slide under barrel opening of the slide and bind it.
More info and pics would be nice.
If the mag comes out and no round in chamber you can pit a cleaning rod through barrel and and tap it loose.
If there is an in fired round it chamber I would try different approach.
If you took thread protector off to test fit the thread adaptor you may have left the recoil spring retaining washer off. That would cause recoil spring or a small part of it to slide under barrel opening of the slide and bind it.
More info and pics would be nice.