The bulk of polarizing filters these days for photographic purposes are so-called “circular polarising filters”, in brief CPL. They consist essentially of a proper linear polariser and a “quarterwave plate” that “scrambles” the polarised light in order to make it mostly unpolarised again. The reason is that parts of camera optics particularly in SLR and DSLR, like beam splitters, phase-based autofocus, separate exposure meters, analog TTL flash metering will fail to work reliably with polarised light.
The quarterwave plate is not perfect but good enough for those purposes. As a result, CPL filters have a “polarised” and an “unpolarised” side in a manner of speaking, with the polarised side turned to the scene and the unpolarised turned to the camera.
For any purposes intended to try blocking light, you thus need to place CPL filters with their front sides facing each other or with the front side turned to (say) a laptop screen.
If you instead use the backside, the polarised light will first get depolarised by the quarterwave plate and then half of it gets blocked by the polariser plate. Since “depolarisation” is not perfect except for a single wavelength of light, you’ll get various hues by rotating the filter then, but no blockage. Orienting it the other way should give you the expected blockage on certain angles.