My CoS / CAS has expired but I have not yet been able to apply for a visa. What should I do?

Home Office guidance confirms that you can still apply for a visa. The start date for the course or employment stated on the CoS or CAS may have changed, and they will not automatically refuse such cases.

They will also not be automatically refusing cases where the CoS has become invalid due to your inability to travel, but they will be considering such scenarios on a case by case basis.