If you are looking to understand your similarity percentage before submitting your work, please use the Test my Text function in Moodle, instead of submitting multiple times. Instructions on how to do this can be found here.
If you submit the same assignment more than 3 times in a 24-hour period, the similarity percentage will then take a full 24 hours to generate.

There can also be delays if there is high traffic in the system. If there is a message saying queued, your similarity percentage will appear when ready. If a red cross appears, you can click on it to refresh again and generate your similarity percentage.

Some file formats cannot be read by Turnitin, a list of file formats is available here.

If you are still experiencing issues, please contact Learning Tech by raising a query via the online IT helpdesk.