It is not that that LPA does not function. It is the fact that you are the legal owner of the property beneficially and also acting as LPA for your husband. When property is owned jointly, the sellers actually sell as Trustees. You cannot be both Trustees at once.
A simple solution is to appoint a legal professional as the second Trustee, simply for the sale of the property. This will satisfy the purchasers (2 trustees are always needed in co-owned property). The new property can still be purchased in your name and the name of your husband.
There are ordinarily no tax implications - it is a straightforward sale and purchase of the principle private residence. Although clearly I cannot comment on your personal circumstances.