Hello, hope all is well. I regret to inform you that this is not the place for connection issues but I will be glad to assist here. If you have not really leveled up your PSOv1 character or if you don't mind starting over, I STRONGLY recommend going to PSO Palace and getting what you need, which is NOT your version of PSO. You need PSOv2 which the PSO Palace will direct you to. Also, find a copy of Dream Eraser, burn it and use it first. Then you need to reset your network connection info on the Dreamcast. Then boot up your newly burned PSOv2 disc and set up your character/SNAK data per the guide.
If you want to maintain that PSOv1 character, then you will need to provide more details as to what is happening.