I recently got a little beer brewing kit to use at home with a 4L fermentation bottle. Up until I filled the beer into the bottle I think I've done everything right, but since then I saw no sign of a fermentation process in the bottle whatsoever. I think I used a bit to little yeast. The color, consistency and the overall apperance of the beer have not changed at all and it's been like 10 days now. Is there any way I can save this "beer", for example if I open the fermentation bottle, fill in some yeast and close it again for a week or is this batch of "beer" completely lost?
Sometimes (rarely and with low gravity table beer) I see very little signs of fermentation. Just a thin layer of krausen on top.
The only way to really know if fermentation has started/finished is to test the gravity to see if any of the sugars have been converted by the yeast you used. If this test shows that the gravity is the same as the starting gravity, then you could pitch a new batch of yeast, appropriately sized for your volume and gravity of wort.
If the test shows that the yeast have begun eating the sugars but the beer has not reached final gravity, I would wait a bit to give the yeast a chance to attenuate fully.
If subsequent gravity readings indicate a stalled fermentation, then I would advise you to search this site for "Stalled Fermentation" There are many good answers here on how to deal with this issue.