It’s most likely that your sourdough starter is not active enough. Temperature can also slow down the rising process, but most likely, your starter was sluggish and not fed enough. Let the starter sit on the counter and see if it will rise. It may just take longer, but if it does not rise, then your starter needs to be revived. To revive your starter, take 1/2 cup of the starter you have, ( don't use more than this) and 1/2 cup water and 1/2 cup flour. Stir all this together and leave on the counter for 8 to 12 hours and feed it again every 8 to 12 hours until really bubbly. Then it will be ready to make bread. Let me know how it does or if you need more help. A sourdough starter is like a pet and you have to feed it and make it strong and then it will rise your bread much better