You mean a replacement SIM or a brand new SIM? Did you activate it? Is it linked to your existing account, membership etc.? What happens if you do a manual search for networks? Can you see and connect to 48? Did you just change SIM or also phone? What make and model of phone is it? If necessary contact 48 support. See the link in my signature below.
BTW it's not a good idea to post a phone number in a public forum like that. You should edit your post to remove it.
Hope this helps.
I am not a 48 employee so if you need to contact 48 support then use option 3 or the chat facility here.