Welcome GE90, and I'm sure help is on the way! It's probably something to do with the automatic setting you're using. It may be limiting the focus via the aperture and shutter speed it is choosing for you. That said, let's see what some fine Panasonic shooters have to say. Hang on!
There could be lots of reasons why the camera won't let you take a photo in iA mode. If you're too close and the camera can't focus on the object you want in Macro mode, if you don't have enough light, if the previous photo hasn't finished writing to your card, etc., etc. Without more details on what you're trying to photograph and your setup it's difficult to say what could be the reason.
When you shoot in iA mode you're at the mercy of some software programmer who made those decisions for you years ago. It's best to start weening yourself off iA mode as much as you can so you can start taking control over your photography. Start my just switching to MF, then slowly migrate to the other modes that give you more control - P, A, S, and M.
What lens do you have GE90? I have the 20mm/1.7 and it is reluctant to focus close up. It can do it though, just the auto-focus tends to focus on the background.
The best option for macro is to use the manual focus mode (button AF/AE), and move the camera physically closer or further away until you have reached focus. You can turn the focus ring on the lens depending on how big you want the object to appear.
You could get a close-up filter, or a macro lens if you want to get closer to your subject.
I would think you should be able to capture most of that card if you simply zoom in to 45mm, then crop the resulting image. You don't need super-high resolution to post photos of items for sale over the internet if that's what you're doing.
Yep, that's the beauty of interchangeable lenses. You get the lens that is appropriate for the job. A dedicated macro lens is ideal for this. However, some other lenses do an okay job as well. The 20mm is not one of them, it wasn't designed to be either.
Your lens will only focus to about 12 inches no matter what way you do it. The minimum distance is across the range of the zoom so at 45MM you will get your largest magnification. I suspect, unless you have a gigantic memory card , you will have to crop to get it t the size you want for display.
In a pinch you can hold a magnifying glass in front of your lens to shoot modest macro images. I set my 14-45 to 45 and held the magnifying glass against the front of the lens to photograph a memory card to illustrate. (Taken with a Lumix GF1 and 14-45mm lens.)