Exhibit 10.6

December 27, 2021

3i, LP

140 Broadway FL 38

New York, NY 10005

Anson Investments Master Fund LP

c/o Anson Advisors Inc. 155 University Ave., Suite 207

Toronto, ON Canada M5H3B7

Anson East Master Fund LP

c/o Anson Advisors Inc. 155 University Ave., Suite 207

Toronto, ON Canada M5H3B7

Dear Sirs:

Reference is made to (a) that certain Securities Purchase Agreement (as modified from time to time, the “Purchase Agreement”), dated as of September 24, 2021, between the Company and the purchasers identified therein, which are the same as the three addressees listed above (collectively, the “Investors”) and (b) the Senior Secured Convertible Promissory Notes (as modified from time to time, the “Senior Secured Convertible Notes”), and (c) and the other transaction documents, as modified from time to time, referred to collectively, as the “Transaction Documents”). Capitalized terms used but not defined herein shall have the meanings given to them in the Purchase Agreement, or if not defined therein, in the Notes, or if not defined therein, in the applicable Transaction Document, in each case as of the date hereof.

This letter agreement (this “Letter Agreement”) confirms our recent discussions about, among other matters, certain modifications to the Senior Secured Convertible Notes.

The Company hereby agrees, for itself and its Subsidiaries, that the Guarantors continue to guaranty, pursuant to the Guaranty, as primary obligor and not as surety, the full and punctual payment when due of the obligations owing under the Notes and the other Transaction Document as modified hereby (as limited by the original terms of the Guaranty) and that the terms hereof shall not affect in any way their obligations and liabilities, as expressly modified hereby, under the Transaction Documents. The Company, for itself and its Subsidiaries, hereby reaffirms (a) all such obligations and liabilities and agrees that such obligations and liabilities shall remain in full force and effect and (b) the security interests granted under the Transaction Documents and agrees that such security interests shall continue to secure such obligations and liabilities.

This Letter Agreement is a Transaction Document and is limited as written. As of the date first written above, each reference in the Purchase Agreement or any other applicable Transaction Document to “this Agreement,” “hereunder,” “hereof,” “herein,” or words of like import, and each reference in the other Transaction Documents to such Purchase Agreement or other Transaction Documents (including, without limitation, by means of words like “thereunder,” “thereof” and words of like import), shall refer to the Purchase Agreement as modified thereby, and this Letter Agreement and the Purchase Agreement shall be read together and construed as a single agreement. The execution, delivery and effectiveness of this Letter Agreement shall not, except as expressly provided herein, (A) waive or modify any right, power or remedy under, or any other provision of, any Transaction Document or (B) commit or otherwise obligate any Purchaser to enter into or consider entering into any other amendment, waiver or modification of any Transaction Document.

All communications and notices hereunder shall be given as provided in the Transaction Documents. This Letter Agreement (a) shall be governed by and construed in accordance with the law of the State of New York, (b) is for the exclusive benefit of the parties hereto and the other Purchasers and beneficiaries of the Purchaser Agreement and, together with the other Transaction Documents, constitutes the entire agreement of such parties, superseding all prior agreements among them, with respect to the subject matter hereof, (c) may be modified, waived or assigned only in writing and only to the extent such modification, waiver or assignment would be permitted under the Transaction Documents (and any attempt to assign this Letter Agreement without such writing shall be null and void), (d) is a negotiated document, entered into freely among the parties upon advice of their own counsel, and it should not be construed against any of its drafters and (e) shall survive the satisfaction or discharge of the amounts owing under the Transaction Documents. The fact that any term or provision of this Letter Agreement is held invalid, illegal or unenforceable as to any person in any situation in any jurisdiction shall not affect the validity, enforceability or legality of the remaining terms or provisions hereof or the validity, enforceability or legality of such offending term or provision in any other situation or jurisdiction or as applied to any person.

This Letter Agreement is expressly conditioned on the following conditions precedent:

Kindly confirm your agreement with the above by signing in the space indicated below and by PDFing a partially executed copy of this letter to the undersigned, and which may be executed in identical counterparts, each of which shall be deemed an original but all of which shall constitute one and the same agreement.