Welcome @curmudgeon1 .
I believe it is by design that the tutorial you used (menu Help-Tutorials-Operation Tutorials-Jet Cutting) reset the material and machine dimensions since setting them is included in the tutorial steps, on page 2. Follow those steps and it should correct the issue.
Alternatively, menu Options-Job Options on the Material tab will set dimensions of the maroon material background. menu Options-Machine on the ‘Work envelope’ and ‘Table display’ will set those dimensions, but I prefer to just leave them 0,0.
tip: once you get material and other Job Options established, including some tool definitions, you can create a job template of those settings that can be quickly reloaded to return to those states. See menu File-‘Save job as Template’.
When you finish those tutorials, see also-