EIS3 claim form timeline

Hi, I submitted an EIS3 claim form which is showing in my online account as received 22nd February 2024. I have since chased via phone for an update and each time I am told my claim has been assigned to someone and it'll be looked at by a certain date (usually 3 or 4 weeks from the date I call). I called again last week, being 2 weeks after the most recent expected assignment date and was told that the team has not picked up the assignment yet and so no estimation of time frame can be given. How can I escalate this further? Waiting for over 5 months for a claim, still with an open ended resolution date, surely is not typical. Any pointers on next steps would be appreciated. Thanks

Hi,
You can progress chase your EIS claim by telephoning 0300 200 3300 if you complete a self assessment tax return, you can also contact our Self Assessment team below.
Self Assessment: general enquiries
If you wish to make a complaint you can do online at:
Complain about HMRC
Thank you.