Did you give the owner a preliminary notice? When did you record the lien? You have 90 days to file suit after recording the lien. Also, before you could have recorded the lien, you had to serve the preliminary notice within 20 days of commencing work. Assuming, you have recorded the lien properly and you gave the required notice to the owner. You should not sign a release unless you are paid. Has the owner given you a reason, other than the contract with the tenant?
Did the property owner post and a "Notice of Non-Responsibility" on the property? The owner was obligated to both post and record a Notice of Non-Responsibility within 10 days of learning there was work being performed on the property.
This answer does not constitue legal advice, nor does it creat an attorney/client relationship. If you are seeking legal advice upon which you intend to rely, you should hire competent cousel familiar with this area of the law in your locale.
This is a very technical area of the law and you really need to sit down with a construction lawyer in your area to discuss your remedies. A mechanics' lien can attach to a leasehold interest in real property, and even if you can not sue to foreclose on the real property itself, you may be able to sue to foreclose on the leasehold interest. That lease may or may not be worth anything, depending on the length of the lease and the nature of the improvements. Do you know if the property owner record a Notice of Non-Responsibility before construction started? Even if they did, there is a "participating owner" doctrine in the law that, if applicable, could hold the owner responsible to the same degree as the leaseholder. Also, most leases require that the leaseholder maintain the property "lien free", and so the tenant will be in breach of the lease if they don't resolve your lien. The property owner should be pressuring the leaseholder to resolve the lien and not pressuring you. Again, this is a very technical area of the law and really requires sitting down with a construction lawyer in your area.
Construction projects and the legal rights and remedies that flow from them are legally technical and factually intensive. This Avvo answer is not legal advice and should not be relied upon without further consultation with a qualified construction lawyer.
You may have lien rights against the tenant's lease and not the property as whole depending on the facts here. You need to know if the owner posted and recorded a Notice of Non-Responsibility. I agree this is complicated and that you should talk to an experienced construction attorney right away.
Having had the benefit of reading your comment in response to another attorney's questions, if you have not filed a lawsuit within 90 days after recording your lien, you have lost your right to enforce your lien with a lawsuit. You still may be able to collect from the tenant by filing a lawsuit for breach of contract or some other claims, depending on what agreement(s) you had with the tenant.
Based upon your response to one of the comments (recording the lien in April), unfortunately you have exceeded the 90 day period in which to bring a legal action to enforce the mechanic's lien. As to whether or not you have any basis to bring legal action against your client, the tenant, you need to contact an attorney to review all of the issues involved, including defenses that could be asserted by your client.