you have a few options here: do as suggested above, increase pressure and leave for a couple of weeks or if it is ready to drink you could force it quicker…
There are methods to do this in a few hours, days or weeks, less if you want to rock it. If you have the space to lay the keg flat at lagering temperature one option is whack it up to 45psi and either keep connected or return several times to top up as theCO2 is absorbed. Apparently giving it more surface area helps the absorption. I have tried this method over a 6 hour period with a 1L pet bottle and it does work, but not tried on a corny.
There are methods to do this in a few hours, days or weeks, less if you want to rock it. If you have the space to lay the keg flat at lagering temperature one option is whack it up to 45psi and either keep connected or return several times to top up as theCO2 is absorbed. Apparently giving it more surface area helps the absorption. I have tried this method over a 6 hour period with a 1L pet bottle and it does work, but not tried on a corny.