Cubase Pro 10.5 Video Player play back issues

I am ‘having a go’ at putting music to a video clip for the first time. The clip is mp4.
The clip was ‘mismatched’ so I went into project/project setup/get frame rate from video and this set it to 29.97 I then opened video player (F8) but the video wont play. It starts for a fraction of a second then sticks. The timecode works ok. Any clues. Is it something to do with codecs which I know nothing about!

Operating System
Windows 10 Home 64-bit
Intel Core i7 7700 @ 3.60GHz 31 °C
Kaby Lake 14nm Technology
64.0GB Dual-Channel Unknown @ 1069MHz (15-15-15-36)
LG HDR WFHD (2560x1080@59Hz)
Intel HD Graphics 630 (ASUStek Computer Inc)
238GB SAMSUNG MZVLW256HEHP-00000 (Unknown (SSD))
931GB Samsung SSD 860 EVO 1TB (SATA (SSD)) 31 °C
931GB Seagate ST1000DX002-2DV162 (SATA ) 26 °C
3726GB Samsung SSD 860 EVO 4TB (SATA (SSD)) 23 °C
29GB ADATA USB Flash Drive USB Device (USB )


Please read through Video support in Nuendo, Cubase, WaveLab and Dorico article.

Thanks for the reply Martin I will check it out. Thank you.

Hi Martin.
I checked the link and it was of great service. Where it suggested downloading recommended encoding setting, I downloaded AVID MEDIA COMPOSER (free version) and after some helpful YouTube tutorials I saved my unplayable mp4’s through AMC as H.264 files (they were h.264 before but obviously something else was amiss) and when I put them back into Cubase they played fine.
It’s taken quite a few hours to get to this point but it was worth the effort.
Thanks for your help and hope this can help others in a similar situation.