Trigger a Speedlite 430EX II with a studio flash

Possibly the sync speed set the camera on 1/80 sec and retry

this is most likely a sync issue. you shutter speed is too high. try lowering it. 1/200 or 1/160 of a second should be fine for your case.

Make sure you using flash grade batteries and not rechargables. try energiser ultra or litiums or duracelll plus but nothing else. if the charge light is not coming up then most likely batteries. I would take it to your local camera shot and test your 7d with one of thier 430 just to make sure the hotshoe didnt short out the flashgun

No. You will need an EX series flash like the 430EX or 580EX. Those designated as EX II will also work.

No. The rebel, or any digital canon camera requires the use of the EX or EX II series flashes.

The hot shoe was bent slightly causing the flash contacts to not touch those of the camera. By using a socket from a socket wrench set, place it over the grids of the hot shoe and tap firmly with a hammer to straighten it.

I assume that flash is turned on. 430ex flash will fire automatically only in AUTO mode. On manual modes you mus manually force the flash to fire.
If flash doesn't fire at all, consider to claim the vendor or let the vendor to check the flash mounted on your camera.

The camera in P mode does not allow the pop-up flash to work until you turn it on. Make sure the camera is in green box mode and if the flash does not work then the camera will have to be sent to canon for service.

I also own a Vivitar 285 that i used with my Canon F1 manual 35mm camera. Most older cameras before the advent of digital, had a hot shoe on top of the camera, or like in my case, the hot shoe went over the rewind knob. I also had to plug in a power cord from the 285 flash foot and the cameras PC connection in order for the flash to work on some other cameras. The Canon Rebel XTi has a TTL (through the lens) hot shoe usable with Canon's own EX flash units. You can buy a "hot shoe to PC connector" if the TTL camera hot shoe doesn't work, but be extremely careful, the only problem that exists with the older manual flash units was the trigger voltage is as high as 200+volts which would fry digital camera hot shoes. I tried my unit with a Wein flash trigger device on the PC cord of the flash and my Canon D60 with it's own flash. All shots were overexposed and washed out highlights.  Here's a copy of the hot-shoe review:h The EOS 400D's hot-shoe can be used with Canon and third party flashes (although sync only on most third party units). The hot-shoe is E-TTL II compatible. Compatible flashes include Speedlite 220EX, 380EX, 420EX, 430EX, 550EX, 580EX, Macro-Ring Lite, MR-14EX, Macro Twin Lite MT-24EX and Speedlite Transmitter ST-E2.  The Canon Rebel XTi doesn't have a PC socket to plug in a manual flash trigger cord which common sense tells me there is no provision to step up the voltage to trigger manual flashes - so my answer is this combination is not a good idea on a Canon Rebel XTi. Hope this helps.

ALL Canon digital EOS cameras will work with E-TTL only. Solution: you need EX flash for full auto.