You didn’t provide release details, but I’m betting your release isn’t a supported release which is your problem.
A query on versions available does not show that version available, either the standard or ESM support releases ie.
guiverc@d960-ubu2:~$ rmadison gparted
gparted | 0.18.0-1 | trusty | source, amd64, arm64, armhf, i386, powerpc, ppc64el
gparted | 0.25.0-1 | xenial | source, amd64, arm64, armhf, i386, powerpc, ppc64el, s390x
gparted | 0.30.0-3ubuntu1 | bionic | source, amd64, arm64, armhf, i386, ppc64el, s390x
gparted | 0.30.0-3ubuntu2 | bionic-updates | source, amd64, arm64, armhf, i386, ppc64el, s390x
gparted | 1.0.0-0.1build1 | focal | source, amd64, arm64, armhf, ppc64el, riscv64, s390x
gparted | 1.3.1-1ubuntu1 | jammy | source, amd64, arm64, armhf, ppc64el, riscv64, s390x
gparted | 1.3.1-1ubuntu1 | kinetic | source, amd64, arm64, armhf, ppc64el, riscv64, s390x
Your issue is your release is unsupported, what are you using? is it impish or 21.10?
impish (21.10) (gnome): GNOME partition editor
1.2.0-1ubuntu2: amd64 arm64 armhf ppc64el s390x
https://packages.ubuntu.com/impish/gparted
To upgrade, refer https://manual.lubuntu.me/stable/D/upgrading.html
but given you’re now late, you may also need to change your mirror so it uses the old-releases archive, and remove any country codes, as documented here - EOLUpgrades - Community Help Wiki
(how many extra hoops you need to jump thru will depend where you are in the world, what mirror if any you’re using etc. as mirrors can drop an EOL release anytime after it has reached EOL, so it maybe gone already for you, or parts still remain)