Tenant not responding to communications

Access

We have a tenant who we served a section 21 notice to in Wales on 29th January. we understand that due to current circumstances this can't go forward until the courts resume. however the tenant is £2833 in arrears and has refused access for the gas certificate to be carried out. She is not returning our calls and does not acknowledge written communication or makes excuses that she will not be home. we need to carry out repairs to the roof but need access to the loft space to check if any work needs carrying out internally. The local council housing officer advised the tenant to stay in the property and not move. The council have informed me that if I put a letter through her door, with photographic proof, giving at least 24 hours notice if she is not at home at the appointed time we are legally able to enter the property. - is this the case please.