This study is for patients that have been diagnosed with advanced or resistant skin cancer (melanoma), non-melanoma skin cancer (NMSC), non-small cell lung cancer (NSCLC), certain types of solid tumors, or bladder cancer (UBC). The investigational drug in this study is RP1. RP1 is a herpes simplex virus (a microscopic life form commonly known as the "cold sore virus") that has been genetically changed to grow in and destroy cancer cells. This treatment will be injected directly into tumors. The purpose of this study is to test the safety and how well RP1 works when it is injected into certain types of solid tumors in combination with another cancer drug, called nivolumab. Participants can expect to be in this study for about 2 to 3 years.