Leverkusen won the match 2-1 thanks to a Kiessling header which went in through a hole in the side-netting.
Hoffenheim appealed against the result, but the German FA's (DFB) tribunal ruled following a hearing in Frankfurt on Monday that the original result would stand.
Tribunal chairman Hans E Lorenz said that referee Felix Brych did not break any rules in making his decision.
He said: "The decision may be unsatisfactory in sporting terms, but is in line with the rules and regulations."
Brych, who awarded the goal, told the hearing: "I thought that the ball was going wide. I lost it because my line of sight was obscured, And then I saw, the ball was in the goal."
Brych said he gave the goal, which put Leverkusen 2-0 up in a match they won 2-1, after consulting with his assistant.
Kiessling, who has come in for criticism for accepting the goal, did not see the incident clearly because his view was also blocked, but assumed that Hoffenheim goalkeeper Koen Casteels must have helped the ball into the net.
The striker said: "I saw the ball fly in the direction of the side-netting. My view was blocked and I did not see the impact, but the ball was in the goal.
"My first thought was that the goalkeeper had turned it in himself. I thought of everything, but not really of a hole in the net."
Hoffenheim have a week to decide whether to appeal further.