If a supplier stops shipping product to a company, then that's a bad thing. If that stop lasts for five months straight, then little surprise here that things are tight at Tetenal. Nobody here knows (or at least posts publicly) the reason for that supply stop, it may be unpaid bills, it may be technical problems, it could be anything. At this point we can only resort to wild speculations.
Henning already stated, that this is an "Insolvenzplanverfahren in Eigenverwaltung", which means, that in accordance with the creditors the original management tries to resolve the financial issues while the company typically continues operations. While the word "insolvency" sounds all bad and scary, there appears to be some expectation on the creditor side, that this company can be turned into a profitable outfit by its own people.
From all this I'd conclude, that Tetenal is here to stay, at least for now.