The former vice president is to appear in the inquiry into Trump’s attempts to undermine the outcome of the presidential election. On the day of the assault, Pence had to ratify that election result, in his role as president of the Senate. Trump and his supporters wanted him not to because they believed the election had not been fair. Pence does not have to answer questions about his role.
It is one of many investigations and cases pending against Trump. The former president’s previous attempts to block testimony have already failed, so the chances that he blocks Pence’s testimony are slim. The former vice president himself did not appeal the call to testify.