He tested positive for the prohibited substance betamethasone after undergoing treatment for his back injury, which he got during training.

On 30 March 2021, he set a national record of 10.01 seconds in the 100 m in winning a meeting at Yabatech Sport Complex in Lagos, Nigeria.

[5] At the 2020 Tokyo Olympics 100 metres semi-final in August that year, he set a new national record of 10.00 seconds.

[7] In September, he ran 9.77 seconds (+1.2 m/s) for a new African record at the Absa Kip Keino Classic held in Nairobi, Kenya coming in a close second place behind Trayvon Bromell, who ran a world-leading 9.76 s.[8] In June 2022, Omanyala became African 100 m champion before he was eliminated in the semi-finals of the World Championships held in Eugene, Oregon, in July, after arriving at the event only a couple of hours before his first round heat due to visa problems.

[10] Omanyala served as Kenya's flag bearer alongside Triza Atuka for the opening ceremony of the Paris games.