If you get an issue when trying to load a task sequence and you get the message that a package associated to the task sequence cannot be found, even when it looks like all packages are fully distributed, then you need to check out the SMSTSLog.log file that is on the machine that you are trying to deploy the task sequence to.
To do this, you must have the command prompt via F8 turned on.
Go into a command prompt by pressing F8 and then go in the root of your X: drive. From here type:
Cd %temp% and press enter
Then go into the SMSTSLog folder by typing:
Cd SMSTSLog and press enter
You can then see the SMSTSLog.log file, however, you want to be able to open it up in trace32.exe so that you can view the errors. For me, the best way is to map a network drive to a share, then copy the file to that share on then open an another machine that has trace32.exe installed, from here, you should be able to find the package ID that has the problem, update the distribution of this package and then your task sequence should run without issues.