The manual that came with my Instant Pot says not to put the lid in the dishwasher. The Instant Pot website says that the lid is dishwasher safe. Which should I believe?
If you only have 2 conflicting pieces of information I'd choose the safer route and not put it in the dishwasher. The manual is specific to your model while the website is not. If you trawl through forums you'll probably find that there's experience out there on the subject.
The manual might have been written earlier or later compared to what is on the website - the manufacturer might have empirically found the lid to be dishwasher safe (or unsafe) after the earlier set of instructions was written.
Also, such information might be in an regional context. One statement could be for a region where typical dishwasher designs or detergent formulae are more aggressive. Or, the typical tolerance for cosmetic damage might be regionally different. Or, there could be a residual risk of the lid and its safety features failing catastrophically (I am not claiming there IS!)- and the liability risk if that happens might be very different from region to region.
Also, there might have been a manufacturing change without changing the model number, causing an earlier or later batch to be safe/unsafe in the dishwasher.
If in doubt, contact customer support for that manufacturer, hold model and serial number ready.