Hi, I have assembled an edited video file on the timeline, when I try to render it, it always hangs at 99% and will not complete, it is very frustrating as I have tried it seven times now.
I am using Linux Mint on my computer.
Please can anyone help, thanks Geoff.

Strange, I have never had something like this.
Have you tried to render to some other format/using another codec?
Sometimes it can be a good idea to render a project to a lossless format first and then "convert"-render it to the final format.

Well I am just guessing here.

First, I'd make sure that your project profile matches the properties of the video clip(s), like resolution, frame rate and so on. I think it is important that all video clips in one project have the same frame rate.

It can be a good idea to transcode a video before editing it. To my knowledge this also allows to change the frame rate of a video if necessary. You can transcode a clip by right-clicking it and choosing Transcode, then choose the required resolution, frame rate and bitrate. DNxHD is a great format for editing and almost lossless. I think best is to only change frame rate if necessary and otherwise avoid it. But some video players and websites like YouTube don't handle/accept frame rates higher than 30 fps.

Once you have your clips transcoded and they match the project profile, you can edit and render, and there should be no problem. If there still is a problem when rendering, I would try what I suggested in my previous reply:

Try to render to a lossless format first. Of course lossless does not mean that rendering works without problems, but there is a chance that rendering works fine, and then you have a video without quality loss that you could "convert" to your final format, maybe even with another tool.
In the render dialog, choose Lossless/HQ as target. Then choose for example "FFV1 lossless (video) + FLAC (sound)". This creates a very big file, so make sure to have plenty of disk space available. See if rendering works like that. It will probably not be possible to play this video, but you can add it as a clip to another kdenlive project and simply render it to the final format you want (H.264, ...).
But it is really just a guess. Maybe rendering already works when you choose another format, I recommend H.264, it is highly compressed, good quality and widely supported.