There may always be the possibility that, that Presto card is simply not compatible with the LCIII+. It's certainly compatible with the LC and Classic, and probably LCII, but I've seen no information any where about that card working successfully in a LCIII+. There are a few facts here that point in that direction -
1/ The card 'supposedly' came from working in a Mac Classic, if that's true, then it does suggest the card was working.
2/ Sonnet brought out another, faster card, the Sonnet Plus, that is known to work successfully with the LCIII+, was this possibly because the previous one didn't?
3/ You cannot get it to work in your machine. The X through the extension is saying the driver isn't loaded, presumably because it cannot see the card.
4/ When the machine boots and the driver doesn't load, the machine hangs or crashes.
I would try one more thing. Install System 7.1, strip it of all but essential control panels and extensions, make sure virtual memory is switched off and 32 bit addressing is switched on (if you've got that option in the Memory control panel) reboot the machine and zap the PRAM. Make sure the RAM simm is out and you're using motherboard RAM and take out all the VRAM simms. If it still hangs or crashes or the driver doesn't load, you can only assume I think that it's simply not compatible with that machine.
1/ The card 'supposedly' came from working in a Mac Classic, if that's true, then it does suggest the card was working.
2/ Sonnet brought out another, faster card, the Sonnet Plus, that is known to work successfully with the LCIII+, was this possibly because the previous one didn't?
3/ You cannot get it to work in your machine. The X through the extension is saying the driver isn't loaded, presumably because it cannot see the card.
4/ When the machine boots and the driver doesn't load, the machine hangs or crashes.
I would try one more thing. Install System 7.1, strip it of all but essential control panels and extensions, make sure virtual memory is switched off and 32 bit addressing is switched on (if you've got that option in the Memory control panel) reboot the machine and zap the PRAM. Make sure the RAM simm is out and you're using motherboard RAM and take out all the VRAM simms. If it still hangs or crashes or the driver doesn't load, you can only assume I think that it's simply not compatible with that machine.