Cappis started to play soccer for academy club, Texans SC. In 2017, his club won the『2016–17 US Developmental Academy U17/18 Championship』with him being named "Central Conference Player of the Year".
As a result of his performance on this tournament, he and Chris Richards, who was also part of the team, were approached by FC Dallas's academy and in the same year, they signed with the club. After several good performances at the Dallas Academy, the club showed interest in sign him a professional contract. However, the move was prevented by MLS due to the Homegrown Player Rule which prevents academy players from signing with clubs far from their native town. As Cappis is from Greater Houston, Houston Dynamo was supposed to have priority in signing the player.[1][2]
However, instead of signing with any team on MLS, Cappis went to trial with several clubs in Europe. On November 6, 2018, he signed his first professional contract with Danish Superliga team, Hobro IK.[3][4] On the same day, he debuted for the team in a match against OB at the 2018–19 Danish Cup. Cappis started the game and provided an assist in his team's 4–2 defeat, before he was replaced in the 56th minute by Edgar Babayan.[2][5] On February 10, 2019, Cappis debuted in the Danish Superliga when he replaced Martin Mikkelsen at the 88th minute of a match against AC Horsens.[6] Cappis scored his first goal on March 8, 2020, for Hobro.[7]
At the end of the 2019–20 season, Hobro was relegated to the Danish 1st Division.[8] In December, Hobro failed to renew Cappis' work permit and lead to Cappis' passport being revoked and at facing deportation form Denmark.[8]
Cappis signed a four-year contract with Danish Superliga club Brøndby in February 2021 starting July 1, 2021. He joined the club ahead of the 2021–22 season.[9] He made his debut against AGF on 18 July, coming on as a second-half substitute for Rezan Corlu in a 1–1 draw.[10][11] Cappis scored his first goal for Brøndby in a 2–2 draw against Vejle on 1 August.[12][13]
On 1 September 2023, Cappis joined Norwegian Eliteserien side Molde on a loan deal for the rest of 2023.[14] However, he only got 45 minutes of playing time spread over four matches before returning to Brøndby at the turn of the year.[15]
Cappis was called up to the United States senior squad in January 2020 for a friendly against Costa Rica but did not appear in the match.[16] He received another call-up in March 2021 for two friendly matches against Jamaica and Northern Ireland, respectively, with both games taking place in Europe.[17]
