You have protection here given that you are a consumer and there is an Ombudsman to ensure your consumer rights are protected.
You are covered under the Sale and Supply of Goods and Services Act 1982 here which means you have a right to expect a service (from the insurer) carried out with reasonable care and skill. Furthermore, the policy should be “fit for purpose” and “as described”. If it isn’t then you can allege breach of your consumer rights and breach of contract.
You should now make a formal complaint and if that does not resolve the matter ask them for a "deadlock letter", which is a letter giving their final response. Their complaints details will be on their website.
Once you have the deadlock letter the next step would be to escalate this to the Financial Services Ombudsman - they will investigate and liaise with the insurer which would hopefully result in a reinstatement of cover under the policy. They can order the insurer to make a financial award for inconvenience if they have acted poorly.
Once you have their final response, you can make the complaint here : https://www.fspo.ie/make-a-complaint/
Based on the circumstances, assuming the insurer does not uphold your complaint, I am sure the Ombudsman will do. The Ombudsman will look at this case independently and will make a decision based on what happened. Their decision is binding on the insurer. If the Ombudsman did not find in your favour, therefore, you then have the option of suing the insurer for breach of your consumer rights and you have up to 6 years to bring a claim to the court (the limitation period is 6 years from your date of loss, to when you need to issue a claim).