The body of the victim was found in his apartment in December 2015 and had been there for some time.
Medical experts established that he had been murdered, but since then the investigation has come to a standstill and the killer has not been caught.
On Thursday Solothurn police launched an appeal for witnesses and published a photo of the victim, offering a reward of 10,000 francs for information leading to the arrest of the murderer.
Anyone with information is requested to call 032 627 7111 or email [email protected]