Hi cepwin,
If you want to test your print developer, take a piece of photographic paper - a test strip will do - and expose it under white light for several minutes. Then develop it as normal. If the paper doesn't turn deep black within five minutes, your developer is exhausted or there's something wrong with your process.
Are the negatives fixed properly? Poorly fixed negatives will cause reduced print contrast.
Are you using variable contrast (VC) paper? If so, are you using the correct grade filter in the enlarger? Yellow is soft, magenta is hard. If not, you might not achieve a full black in the image. VC papers can give flat results if you use no filter, especially under a diffusion enlarger.
Are you using a graded paper? If so, are you using the correct grade (see above). Graded papers don't respond to filters but will be contrastier under a condenser enlarger.
Are you developing the paper for long enough? If not you won't attain a full contrast range. At 21 degrees Celsius you should leave resin-coated paper for at least two minutes and fibre paper for five minutes, and perhaps longer to attain those deep blacks. Likewise don't be tempted to 'pull' your prints before they've fully developed. instead, control the exposure time and intensity properly.
Is your developer warm enough? Cold developer will not work as quickly as warm developer and you may underdevelop your paper.
Is the enlarging lens, filter(s) and light path free of foreign material (dust and grease)? Muck and grease on the lens is a common cause of reduced contrast in printmaking.
Lots of things can reduce print contrast. I hope you discover the cause and don't feel discouraged because we all learn from our mistakes and we all start out making them.
Cheers,
kevs.