Arbitration is supposed to give both sides a fair hearing, but it also cannot be allowed to grind to a halt simply because one party decides not to cooperate. Section 25 of the Arbitration and Conciliation Act, 1996 addresses exactly this problem under the heading of default of a party, and it treats the claimant's default and the respondent's default differently depending on what each default would otherwise achieve for the defaulting side.
If a respondent could simply refuse to file a defence and thereby force the tribunal to either shut down the case or accept the claimant's story automatically, that respondent would have every incentive to stay silent whenever the claim was weak on paper but strong on the pleadings alone. Section 25(b) closes that loophole. It tells the tribunal to keep going with the proceedings, so the case still gets decided, but it also says the tribunal must not read the missing defence as an admission of what the claimant has alleged.
That means the claimant is not let off the hook of proving its case; it still has to establish its claim on the evidence before the tribunal, just as it would if the respondent had shown up and contested every point. The respondent's absence changes nothing about that burden.
So under Section 25(b), when the respondent fails without sufficient cause to submit a statement of defence, the tribunal must continue the proceedings without treating that failure as an admission of the claimant's allegations.