I was playing Dark Souls II on my pc a lot. After about 200 hours of ingame time I found that I cant summon or invade anybody. I tried new characters and reinstalling but it didn't help. So any tips, and reasons. P.S. I didn't used any cheats.
As in the question I linked above in the comments, there are several things to consider when attempting to determine why you are unable to summon/be invaded.
1. You are offline.
This is highly unlikely, but it's still a possibility. Just keep an eye on your connection when you want to summon someone, and make sure you are not offline.
2. Your ports are blocked.
This is the more likely situation. You may be online, but your ports aren't open, therefore your firewall is blocking your connection with the rest of the online community. Here is a relevant list of ports to open
3. It's a Soul Memory mismatch
You said that you believe this is unlikely, however you also stated that you can be summoned, though only rarely. Here is a list of general Soul Memory levels per area, though this is just a guideline.
4. You're in the CoC
Again, unlikely. The Covenant of Champions does block coop summoning capability, but it should also block NPC summons as well, and it should also increase your likelihood of being invaded. From what you have reported, this doesn't match up. Nevertheless, you can still easily check. If you are in the CoC, next to your stat bars (health and endurance) you should see this icon.
If you are in this covenant, you can leave by talking to Shalquoir
5. You have been disconnected from online play, as punishments for d/c while being invaded.
Again, the effects are similar to CoC - removing coop summoning, increased chance of invasion. I'm not sure if this affects NPC summoning however. To fix this, there is an item called the "Bone of Order". If you can use this item, this is most likely the case, as you can only use it once you have been "punished".
You can gain additional Bones of Order in NG+ from the Falconer enemies in Things Betwixt.
I hope you find something to solve your problem!